'20/20' REPORTS ON KILLER CLOWN COLD CASE FOLLOWING THE FIRST ARREST AND MURDER CHARGE IN 27 YEARS

Report Includes Interviews with Victim's Mother and Stepfather and with Women Who Say It's Likely That They Sold Clown Costume to Alleged Killer

'20/20' Airs on the West Coast Saturday, October 28 (10:00-11:00 p.m. PST), on ABC

A person dressed in a clown costume offering flowers and balloons shot Marlene Warren on the doorstep of her home. She died two days later - a shocking tragedy that paralyzed a well-to-do community in Palm Beach County where safety and security were taken for granted. Last month, police arrested Marlene's husband's new wife in a cold case nearly three decades old. "20/20" reports on the shocking story and new developments featuring interviews with Marlene's mother and stepfather, Shirley and Bill Twing; and correspondent Deborah Roberts sit down with Deborah Offord and Barbara Castricone, who say there is a strong possibility the alleged murderer bought the clown costume at their shop. The hour also includes interviews with law enforcement, neighbors and reporters who covered the crime. Due to the college football broadcast schedule, "20/20" airs on Saturday, Oct. 28 (10:00-11:00 p.m. PST), on ABC. (Rebroadcast. ABC OAD: 10/20/17)

On Saturday, May 26, 1990, when Marlene was shot, her son Joe, 22 years old at the time, was in the house with friends. Investigators searched for Marlene's murderer, tracking down where the clown costume, flowers and balloons were purchased and locating the getaway car, a Chrysler LeBaron, five miles from the scene of the crime. While investigating Marlene's murder, police became suspicious of her husband, Michael Warren, who allegedly had been having marital problems with Marlene, and his rumored mistress, Sheila Keen, but no arrests were made initially. At the time, Michael and Sheila denied any involvement in Marlene's death. Twenty-seven years later, Sheila, now married to Michael and known to their Virginia suburban neighbors as "Debbie" and "Mike," was arrested and charged with first-degree murder after the case was reopened and authorities said new DNA evidence tied her to the case. Keen Warren has pleaded not guilty, and detectives are still investigating if anyone else is culpable.

"20/20" is anchored by Elizabeth Vargas and David Muir. David Sloan is senior executive producer.