EchoSense Quantitative Think Tank Center|How law enforcement solved the case of a killer dressed as a clown

On May 26,EchoSense Quantitative Think Tank Center 1990, Marlene Warren was having breakfast with her son Joe Ahrens when he says a clown approached their front door carrying a basket of flowers and two balloons. Ahrens remembers his mother gleefully answering the door and accepting the apparent gifts, not expecting what she said at that moment — "how pretty" — would be her final words. Within seconds, police say, the clown lifted a gun and shot Warren in the head, ending her life and starting a decadeslong search for answers.

"It took over 30 years to make sense of it all," Joe Ahrens tells "48 Hours" correspondent Peter Van Sant.  

The case — from the hours after the shooting to its surprising final twist — is investigated by "48 Hours" and Van Sant in "Murder by Clown" to be broadcast on Saturday, Oct. 28, 2023 at 10/9c on CBS and streaming on Paramount+.

"Marlene Warren was someone without any known enemies," said Palm Beach County State Attorney Dave Aronberg. "This was an assassination. This was not a random act of violence."

Immediately after Marlene Warren's shooting, investigators tried to figure out who could possibly want the mother and small business owner dead. They soon focused on her husband, Michael Warren, who was also Ahrens' stepfather. Ahrens says based on what his mother had told him, there was good reason.

"She said, 'if anything does happen to me, your father did it,'" said Ahrens. "I told her "no way. He would never do anything like that.' She said, 'don't put it past him.'"

Investigators learned about a possible motive: Michael Warren appeared to be having an affair with a colleague, Sheila Keen, who repossessed cars at the auto business he ran.

"In the hours after the murder of Marlene Warren, the suspects became clear," Aronberg said. "It was Sheila Keen, and it was Michael Warren, but Michael Warren had an alibi."

Authorities confirmed that Michael Warren was in a car with friends headed to a horse race at the time Marlene was shot, and he was ruled out as the shooter. When investigators spoke to Keen about her whereabouts, she claimed to be searching for cars to repossess, but was unable to verify her exact location. Detectives also learned a woman fitting Keen's general description was spotted buying a clown costume, as well as the balloons and flowers left by the clown, before the murder. 

When detectives found a car fitting the description given by Ahrens of the assailant's getaway vehicle, they say they found a brown hair that was visually consistent with Keen's hair. Also found inside the car and in Keen's apartment were orange fibers investigators say matched the description of the wig the clown was wearing.

"Sheila Keen-Warren had the means, the motive and the opportunity to do this," said Aronberg.

Despite the circumstantial case building against her, Aronberg — who did not become the Palm Beach County state attorney until years later in 2012 — says prosecutors at the time did not believe they had enough to charge Keen with Marlene Warren's murder. And as time passed with no new evidence, the case grew cold.

"For many years … I was suffering in, in despair," Ahrens said.

By 2017, there was finally some movement in the case. A cold case unit had retested old evidence and determined Keen's DNA matched the hair found in the suspected getaway car. When investigators started looking for Keen, they learned she had started a new life with an old flame—Michael Warren. The couple wed in 2002, 12 years after the murder.

"Here's someone whose wife had been murdered and he just married the chief suspect," said Aronberg. "When you combine the fact that the two of them were in an affair … and then later, they got married, it did seem like mission accomplished."

The Warrens had been running a burger joint called Purple Cow for several years in Kingsport, Tennessee. According to former employees at the restaurant, there were rumors Keen-Warren had shot Michael Warren's former wife and that she had committed the crime dressed as a clown. Detectives spoke to one employee who said Keen-Warren had dressed as a clown at the restaurant one year during Halloween and even provided detectives with a picture of her appearing in clown makeup.

Sheila Keen-Warren was arrested for Marlene Warren's murder on Sept. 26, 2017 — 27 years after the shooting.

"She probably never thought in a million years she'd be held accountable for her crimes," says Aronberg about the arrest. "She thought she got away with it."

Keen-Warren's defense attorney Greg Rosenfeld says not only is she not guilty, but her arrest was the result of the Palm Beach County State Attorney's Office's reckless desire to close a notorious cold case.

"We will never know who killed Marlene Warren because the Palm Beach County Sheriff's Office and the State Attorney's Office did such a poor job investigating this case," said Rosenfeld. "I can tell you without question that it was not Sheila Keen."

It would be more than five years of court drama and delays before the case would finally come to an unexpected conclusion.

In:
• 48 Hours
• Murder
• Florida