For more than 50 years, law enforcement finally believes they have found the man who murdered two teens. 19-year-old Diane Olkwitz and 15-year-old Terry Erdmann, the latest cold case cracked using advancements in genetic technology. On November 3rd, 1966, a 19-year-old secretary was found dead inside a factory on Silver Spring Drive in Menomonee Falls, Wisconsin.
She had been stabbed a total of 106 times. Five years later, on June 24th, 1971, the body of a 15-year-old girl was found in a field 2 miles away, stabbed more than 60 times and sexually assaulted. The two cases stayed open for more than 50 years. Then, in 2021, DNA linked the two crimes to the same unknown man.
Her name was Diane Olkwitz. She was 19 years old, the second of six siblings from Menomonee Falls, a village of about 30,000 people in Waukesha County. She worked as a secretary at the Kenworth Manufacturing Plant located on Silver Spring Drive. Diane Olkwitz worked the late afternoon shift in the front office of the Kenworth factory.
The rest of the office staff left each day at 3:30 p.m. Diane stayed behind until 4:30 to accept late deliveries and answer the phone. For 1 full hour every afternoon, she was the only employee working in the front section of the plant. The factory floor was still running on the production side with workers running machines on the other side.
But, the front office where Diane sat was cut off from the factory floor by a hallway and a set of heavy doors. The workers on the factory side couldn’t see or hear what was happening in the office. She was alone in her section of the plant. On November 3rd, 1966, a Thursday, Diane stayed behind at her desk as usual.
At some point between 3:30 and 5:00 p.m., someone entered the building through the front entrance. Diane was attacked inside the office area. She was stabbed 106 times with a knife that the Waukesha County Coroner later determined had a 3 and 1/2 inch blade. The Coroner said the attack went on for several minutes in a room she couldn’t get out of.
A factory worker passing through the front office area at around 5:10 p.m. that evening found Diane on the office floor. She was dead. Blood covered the walls, the desk, and the carpet around her.
“She was pretty much my mentor,”
Her sister Patty said later.
Diane’s younger sisters grew up in the long shadow of what had happened that afternoon on Silver Spring Drive. Her fiance, a man named Donald Hyerlmeier, had been stationed at Fort Hood, Texas completing Army Basic Training at the time of the murder. Donald was deployed to Vietnam and died in combat 2 years after Diane’s murder. He never learned who had taken the life of the woman he was going to marry.
Detectives from the Village of Menomonee Falls Police Department responded to the scene within the hour. The crime scene inside the front office was extensive. Blood and evidence were everywhere. The weapon was not recovered at the scene. In the days and weeks that followed the discovery of the body, detectives canvassed the length of Silver Spring Drive on foot.
They interviewed employees at Kenworth and at every business along the road. They pulled every delivery record, every employee time card, and every visitor log they could get their hands on. Officers went through everyone who had been in or near the building during the hour when Diane had been alone that afternoon.
The investigation covered employees, acquaintances, former boyfriends, traveling salesmen, repair workers, and known violent offenders and sex offenders in the Waukesha County area. Hundreds of people were interviewed individually over the full course of the investigation. They ran fingerprints found at the scene against every available database.
The investigation that continued over the following months produced thousands of pages of documentation. Detectives followed every single lead that came in from the public and from checking with businesses along Silver Spring Drive. After all of that, none of it connected anyone to what was found at the scene.
No arrest was ever made in the Oakwood’s case. The Oakwood’s family stayed in Menomonee Falls. They waited for the phone to ring. They waited for some kind of news from the police department. Any kind of update, >> [music] >> any kind of break in the case. That call did not come for more than half a century.
Four and a half years later, on June 24th, 1971, the body of a 15-year-old girl was found in a field on the northwest side of Milwaukee. The field sat behind a Morway department store in the 10,100 block of West Appleton Avenue, alongside a set of railroad tracks. The area around the field was a strip of open ground between businesses and the neighborhoods farther west.
The girl’s name was Terry Lee Erdmann. Terry was the youngest of three children in her family. She had just completed ninth grade at Samuel Morse Junior High School that spring and was looking forward to starting at James Madison High School in September. Terry lived with her family on West Silver Spring Drive, about a mile and a half from where her body was found.
Terry had been visiting a friend’s house near North 95th Street and West Rio Street the day before. She frequently took a well-worn path through the field as a shortcut to get home. It was faster than going around by the road. The path ran alongside the railroad tracks and cut through the open ground behind the row of stores.
It was a route that local teenagers from the area used regularly to shave time off the walk between their neighborhoods. On the evening of June 23rd, 1971, as Terry made her way along the path toward home, someone came at her on the path or somewhere in the open ground near it. The girl was sexually assaulted and stabbed more than 60 times.
Her body was found in the field the next morning by someone passing through. Milwaukee Police Department homicide detectives responded to the scene the morning the body was found. They canvassed the area around the field and the railroad tracks on foot, interviewed residents of the surrounding neighborhoods, and pulled the records of every known sex offender in the Northwest Milwaukee area.
Investigators talked to residents who lived along the path and in the houses bordering the field, asking whether anyone had seen a man near the field or the railroad tracks on the evening of June 23rd. Officers also checked for any unfamiliar vehicles that had been seen or parked in the area. The sexual assault combined with the sheer number of stab wounds suggested someone who could keep attacking and not stop.
Investigators quickly noted the similarities to the unsolved Olk witz case. The same general area of Menomonee Falls and the Northwest side of Milwaukee, a similar knife, the same pattern of wounds that went far beyond what it would have taken to kill. Two young women in isolated locations where they could be approached without witnesses, but in 1971, there was no forensic method to connect the two crimes through physical evidence.
The similarities were impossible to ignore, but they weren’t proof. Menomonee Falls police worked the Olk witz case on their end. Milwaukee police took on the Erdmann case on theirs. The line between Menomonee Falls and the city of Milwaukee meant the two investigations ran in parallel without being formally linked.
The two departments didn’t talk to each other about it. The Erdmann investigation, like the Olk witz investigation before it, generated the same result. Months and months of work, thousands of pages, every single lead a dead end, and no suspect who could be connected to the physical evidence from the scene.
Two families living in the same part of southeastern Wisconsin had lost their daughters to stabbings within 5 years and 2 miles of each other. One was 19 years old, killed inside the office where she worked every afternoon. The other was 15, killed on a dirt path she used to walk home from a friend’s house.
Neither case was ever resolved. Evidence from each scene was boxed up, sealed, and put away in storage. All the paperwork was archived in the records rooms of their respective police departments. The files sat in two different police departments for decades, collecting dust. In Menomonee Falls, detectives reviewed the Olkwitz file periodically, looking for anything they might have overlooked.
Over in Milwaukee, detectives did the same with the Erdmann file. New officers inherited the case material as older ones retired or transferred. Each new group of detectives read through the reports looking for something, anything that might have been missed the first time around. Those sealed containers continued to sit in storage, waiting for a forensic technology that did not yet exist.
Diane’s sister Debbie had been 9 years old in 1966. She and Patty grew up in the same small community where their sister had been killed, driving past the Kenworth factory on Silver Spring Drive as part of their daily lives. Terry Lee Erdmann’s family carried the same weight on the Milwaukee side of the line. Two families divided by a town line and 5 years between the two crimes, each living with the same unanswered question and waiting for the same phone call that never came.
The break finally came in 2021, more than half a century after the crimes were committed. DNA technology had finally gotten to the point where old evidence could be tested in ways that hadn’t been possible in 1966 or 1971. Investigators submitted the old samples from the Olkwitz and Erdmann crime scenes for testing.
Male DNA from each scene had been collected during the original investigations decades earlier and kept in storage ever since. For the first time, the two samples were compared to each other. The profiles from the two scenes matched. The same unknown man had left DNA at the scene of Diane’s murder in 1966 and at the scene of Terry’s murder in 1971.
What the geography and the wounds had suggested for decades, the DNA now confirmed. One person had killed Diane Olkwitz in 1966 and Terry Lee Erdmann in 1971. The science behind it left no room for doubt. The unknown male’s profile was checked against the FBI’s national DNA database, where DNA from crime scenes is checked against the records of people who’ve been convicted.
If the killer had ever been convicted of a serious crime and had his DNA taken, the system would have flagged him. Nothing at all came back. The man responsible had never once been in trouble with the law. His DNA wasn’t in any database, in any state, anywhere in the country. If the database couldn’t find him, the investigation needed a different approach.
In 2022, the Wisconsin Department of Justice, working alongside the Menomonee Falls Police Department and the Milwaukee Police Department, submitted the DNA evidence to Astri a private forensic lab. Astri scientists went to work on the old samples and pulled enough DNA to build a full profile. That complete profile was then delivered to the FBI’s forensic genealogy team, who searched consumer ancestry databases for relatives of the unknown man.
When a distant relative of the unknown man appeared as a partial DNA match, genealogists used the shared DNA to start building a family tree. They traced the family tree branch by branch, going through old public records, census forms, marriage certificates, and death records. The work took months. Candidates were identified and eliminated one by one as birth records, death records, addresses, and job histories were checked against the DNA.
Branch by branch, the family tree narrowed until it pointed to a single individual. The man had lived in the Milwaukee area in 1966 and 1971. He drove trucks for a living, running delivery routes through the same communities where the two crimes had taken place. Married for decades, he had raised a large family in Wisconsin.
And he had died several years earlier in 2008 without any known criminal record of any kind. Investigators went to a judge and got a court order to dig up his body from the cemetery where he had been buried for 15 years. The remains were carefully recovered and transported to a forensic laboratory. DNA extracted from the remains was compared to the crime scene profiles from both the 1966 and 1971 cases.
The DNA was a match. The DNA recovered from the Olkwitz crime scene in 1966, the Erdmann crime scene in 1971, and the exhumed remains all belonged to the same man. One person, two murders. Two young women dead, 57 years of silence. His name was Clarence Marcus Tappendorf, born on July 16th, 1927. Tappendorf had spent his entire life in southeastern Wisconsin.
He married a woman named Joyce Ludwig and they settled down in the area. For most of his working career, Tappendorf drove delivery trucks for a company called Claremont Transfer, a Milwaukee-based trucking firm. His regular routes took him through Menomonee Falls and the neighborhoods around it in Northwest Milwaukee on a weekly basis.
He and Joyce raised their six children together in the Milwaukee area. Tappendorf attended church regularly, watched his children graduate and start families of their own, eventually retired, and died on January 6th, 2008 at the age of 80. His obituary was published in a local Milwaukee area newspaper. It listed his wife Joyce, his surviving children, >> [music] >> and his grandchildren.
It described a man who had spent his entire working life in one quiet corner of Southeastern Wisconsin. Nowhere in the obituary was there any mention of Diane Olkwitz. Nowhere was there any mention of Terri Lee Erdmann. Clarence Tappendorf was 39 years old when he killed Diane Olkwitz and 43 when he killed Terri Erdmann.
Between those two murders and for the 37 years that followed, Tappendorf went home to his family, went to work, and never got into any trouble with the law. He was never arrested or fingerprinted by any agency and no law enforcement department ever contacted him in connection with any investigation.
Police said publicly that they didn’t know if there were other victims, but the most devastating detail in the case did not come from the DNA analysis or the genealogy work. It came from a single piece of paper, a form that had been sitting in a filing cabinet in the Menomonee Falls Police Station since November of 1966, collecting dust alongside thousands of other pages.
In the days right after Diane’s murder, the Menomonee Falls Police Department did something that should have broken the case wide open. They sent a detailed written questionnaire to every company identified as having made pickups or deliveries at the Kenworth factory. Each form asked the company to list their drivers and say where they’d been on November 3rd, 1966.
Among the many companies that received the form and returned it was Claremont Transfer, the trucking company where Tappendorf had worked. Claremont wrote back and said that as far as they knew, none of their drivers had stopped at Kenworth that day. However, one of their drivers had made a scheduled stop at GM Diesel on that same afternoon.
GM Diesel was located directly across from the Kenworth factory where Diane had been killed. And the driver who made that particular stop was a man named Clarence Tappendorf. The same form also noted that Tappendorf had made a separate stop at Kenworth itself on October 31st, just 3 days before the murder.
The delivery on the 31st would have taken him through the front entrance of the building and past the office area where Diane spent the last hour of every workday. His name had been sitting in the Menomonee Falls police file since the week after the murder, written on a police questionnaire alongside hundreds of other names generated by the canvas.
Just one entry among many. Tappendorf was never once formally interviewed about the crime or asked to account for his movements on the afternoon of November 3rd. In the weeks and months after the murder, detectives focused their attention on Kenworth employees, acquaintances of Diane, and known violent offenders in the area.
For 57 years, the answer to who killed Diane Olkwitz had been right there in the file. The form had placed a man with a name and an employer directly across the street from the crime scene on the afternoon of the crime, and noted that the same individual had been inside the building 3 days earlier.
An interview, a background check, a closer look at where he went that afternoon. Any one of those steps could have changed everything. None of them ever happened. On October 25th, 2023, more than five decades after the first murder and 52 years after the second, officials from four agencies held a joint press conference.
Representatives from the Menomonee Falls Police Department, the Milwaukee Police Department, the Wisconsin Department of Justice, and the FBI all stood together at the podium. The officials announced that Clarence Marcus Tappendorf had been identified as the person responsible for the murders of Diane Olkwitz and Terri Lee Erdmann.
Menomonee Falls Police Chief Mark Waters addressed the room.
“Based on irrefutable physical evidence, it is the official position of the Menomonee Falls Police Department that Clarence Marcus Tappendorf is responsible for the murder of Diane Olkwitz,”
Waters said.
Milwaukee Police Chief Jeffrey Norman addressed the Erdmann case and the department’s commitment to working cold cases regardless of how many years had passed.
“There is no statute of limitations in regards to a homicide investigation,”
Norman said.
“We will work on it whether it is 5 years, 10 years, or 70 years to bring closure.”
Members of the Olkwitz family, Diane’s surviving sisters, were in the room. Debbie, who had been 9 years old when Diane was killed, was now in her mid-60s.
Her sister Patty stood beside her. Terri Lee Erdmann’s surviving family members were there as well. Two families who had never met each other, connected by the same man across two crimes and 2 miles of suburban Wisconsin. For the first time, they stood in the same room. Two families from different sides of a county line, bound together by a name they had each waited more than five decades to hear.
A 19-year-old secretary sitting alone in an office on Silver Spring Drive, answering phones and waiting for the end of her shift. A 15-year-old girl walking a shortcut through a field 2 miles south, heading home alone on a summer evening. The same man behind both. The same kind of knife. His full name written on a questionnaire in a filing cabinet for 57 years, and nobody in all those years ever followed up.
