Gillis was arrested at his home and charged with three murders. Investigators soon said he had also confessed to two older killings, one dating back to 1994.
Published

A rare tire track near the place where Donna Bennett Johnston's body was found led investigators to Sean Vincent Gillis. On April 29, 2004, they arrested him and charged him with her murder and two others.
Investigators arrested Gillis at his home on Burgin Road at about 1:20 a.m. He did not resist and agreed to a DNA swab, and authorities said he confessed at around 7 a.m. He was booked into the East Baton Rouge Parish Prison on three counts of first-degree murder and three counts of ritualistic acts in the deaths of Katherine Hall, 29, killed in January 1999; Johnnie Mae Williams, 45, killed in October 2003; and Johnston, 43, whose body was found on February 27, 2004. According to the arrest affidavit, the State Police Crime Lab identified the brand, model and type of tire from the track, a tire made for only three years and bought only 90 times in the Baton Rouge area. Detectives found that Gillis normally drove a vehicle with those tires. After his arrest, the crime lab matched his DNA to evidence in the Hall and Johnston cases, and the FBI's lab matched it in the Williams case. "That tire track was the first little crack," said Lt. Col. Greg Phares of the East Baton Rouge Sheriff's Office. "Investigators swabbed Sean Gillis and the State Police Crime Lab matched his DNA."
The Joint Homicide Task Force then said a confession by Gillis had solved two older killings: that of Ann Bryan, 81, in her apartment at the St. James Place retirement community in March 1994, and that of Hardee Schmidt, who was abducted while jogging on May 30, 1999. He was charged with first-degree murder in both cases, bringing the number of women he was charged with killing to five. Relatives of at least two of the victims said they had feared the killings would be ignored because of the women's "high-risk" lifestyles. In July 2008 a jury convicted Gillis of first-degree murder in Johnston's death, and when it deadlocked on the death penalty, he was sentenced to life in prison. He also pleaded guilty to the 1999 murder of Joyce Williams and received a second life sentence.
WAFB's sources said Gillis had confessed to eight killings, while the same report said he had made seven taped confessions about women's murders.