When a clown showed up at her door, Marlene was delighted. Moments later, she was dead.

On Memorial Day weekend in 1990, Joe Ahrens, then just 21, was looking forward to a lazy morning spent with friends at his home in Wellington, Florida. His mother, Marlene Warren — a small business owner of 40 — bustled around, ready to start the day.

As Joe and his friends sat around the table, sharing breakfast and watching television, a sudden knock at the door interrupted the peace. Marlene answered, curious to see who it could be calling so early.

When she opened the door, she was greeted by a startling sight: a figure in a bright clown costume, complete with a curly wig and painted smile, holding a bouquet of flowers and a bunch of colourful balloons.

"How pretty!" Marlene exclaimed.

They would be the final words Joe heard his mother speak before a sudden BANG tore through the house. The clown had reached into their pocket, pulled out a gun and, without hesitation, shot Marlene in the mouth, killing her.

Watch: Joe Ahrens remembers key detail to solve mother's murder. Post continues after video.

In a state of shock, Joe rushed to his mother's side, just as the clown turned to leave. For a brief moment, their eyes met — a haunting image that would stay with Joe forever.

"The clown looked me right in the eyes," he told PEOPLE. "They were big and brown." 

This, and a glimpse of the getaway car, would be all he saw of his mother's killer.

Detectives immediately got to work trying to piece together the puzzle. Their first suspect was Marlene's husband, Michael Warren, who was Joe's stepfather — and they had a reason to be suspicious.

"[Mum] said, 'If anything does happen to me, your father did it,'" Joe had revealed, as per CBS. "I told her 'No way. He would never do anything like that.' She said, 'Don't put it past him.'"

Michael, investigators learned, was allegedly having an affair with his colleague, Sheila Keen. She worked at Michael's auto business, repossessing cars.

But he had an alibi. While the clown was standing on Marlene's doorstep, Michael was headed to a horse race with his friends.

The spotlight quickly turned to Sheila, who told authorities she was searching for cars to repossess at the time of the incident – but could not verify her location.

Then, a piece of the puzzle clicked into place.

Ahead of the murder, a woman fitting Sheila's general description had been spotted buying a clown costume, balloons and flowers. Authorities then found a car that fit Joe's description of the getaway vehicle. In it, they found a strand of brown hair that was looked very much like Sheila's hair, as well as orange fibres that matched the description of the clown wig the killer was wearing.

According to Palm Beach County State Attorney Dave Aronberg, Sheila had the means, motive, and opportunity to kill Marlene. Yet there wasn't enough evidence to charge her.

The days went on. Then months; then years. No new evidence surfaced, and the case grew cold. Joe was "suffering in despair", as per CBS.

Describing his mother as a "charismatic person of love" to US TV show 20/20, Joe said that he tried to cope with her unsolved death through alcohol. He quickly fell into depression and addiction before checking into rehab and rebuilding his mental health.

Joe waited decades for closure until, finally, a break in the case occurred. DNA testing proved a match between Sheila and the hair in the suspected getaway car.

Investigators searched for Sheila, and found her married to her alleged former lover, Michael Warren. They had been wed since 2022 — 12 years after Marlene's murder.

Alarm bells rang.

"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.'"

At this time, Michael and Sheila were running a burger place in Kingsport, Tennessee.

Whispered within its walls were rumours that Sheila was the clown killer. One employee even claimed that she had come dressed as a clown one Halloween, and provided authorities with a picture.

Sheila was eventually arrested in 2017 for the murder of Marlene, 27 years after the shooting.

She maintained her innocence. But, after five years of court drama, Sheila pleaded guilty in exchange for a lesser sentence of 12 years. Her attorney, Greg Rosenfeld, said that her five and a half years in custody would count towards that sentence and she could be released the following year on good behaviour.

"I never thought I was going to get a guilty [verdict]," Ahrens told 20/20 after the sentencing. "That was a shock. It just blew my mind."

While he accepted the conditions of the plea hearing, Joe stressed that he never once saw remorse from Sheila.

On Saturday, November 2, 2024, the now-61-year-old was released from prison. But Aronberg said she will "wear the stain of a convicted murderer" for the rest of her life.

Meanwhile, Rosenfeld said, "We are absolutely thrilled that Ms Keen-Warren has been released from prison and is returning to her family. As we've stated from the beginning, she did not commit this crime."

A few days after the plea deal was finalised, Joe visited his mother's grave to share the news.

"I was telling her we finally got truth," he told the ABC. "We finally got closure."

Feature Image: Palm Beach County Sheriff's Office/ABC News.