A Florida man whose second wife is accused of killing his first wife while dressed as a clown almost three decades ago insisted that she is innocent to ABC's "20/20".

On a May morning in 1990, Marlene Warren opened her door Wellington, Florida, to find a clown standing in front of her. The clown wore an orange wig, red nose and white face paint. The killer clown handed Warren balloons and flowers before shooting her in the face. Warren died two days later at age 40.

Police arrested Sheila Keen-Warren earlier this month on first-degree murder charges. She had long been a suspect, but police felt that they did not have enough evidence to make the arrest. Sheila Keen-Warren, 54, was thought to be having an affair with Marlene Warren’s husband, Michael Warren, at the time of the murder. Michael Warren and Sheila Keen-Warren married in 2002.

"This is very serious and very unfair," Michael Warren said of the charges.

DNA evidence helped crack the cold case in 2014, and the state is pursuing the death penalty in the case.

"Any murder’s horrific. It doesn’t matter whether you’re wearing a clown costume or not," Palm Beach County Sheriff’s Sgt. Richard McAfee said after announcing the arrest. "Taking another person’s life is a horrific incident. It just took us 27 years to bring closure to the victim’s family. Murder cases never go away."

Michael Warren, 65, has not been charged in the case, but detectives have not ruled him out. Sheila Keen-Warren was arrested in the Virginia home she shares with Michael Warren before being extradited to Florida.

Prior to this year the police had several leads but hadn’t had anything definitive. Several employees at a local costume shop described a woman looking like Sheila Keen-Warren purchasing a clown costume. One of the balloons from the attack had the words "You’re the Greatest" on it and was only available at one supermarket nearby.

Marlene Warren and Michael Warren were having marital problems, according to her family who described them to the Palm Beach Post in 2000. Marlene Warren reportedly told her mother: "If anything happens to me, Mike done it."