A 20-year-old man accused of fatally shooting five people at a Macy’s store in a Washington state mall last year was found dead in a jail cell, authorities said.

Jail personnel found Arcan Cetin unresponsive Sunday evening and began multiple lifesaving measures, including CPR, but were unable to revive him, according to a news release from the Snohomish County Sheriff’s Office.

He is believed to hanged himself, Skagit County prosecutors told the Seattle Times. The death remains under investigation.

Cetin had recently been transferred to the Snohomish County Jail from Skagit County Corrections to await the results of a second mental competency evaluation. The transfer also was made because Cetin had made legally compromising comments about his criminal case to fellow inmates, Bronlea Mishler, the county’s communications coordinator told the Seattle Times.

The inmate “did not let justice take its course,” Skagit County Prosecuting Attorney Rich Weyrich told the Skagit Valley Herald. “Some may have a great relief that it’s over; some may feel cheated.”

Cetin was accused of shooting a teenage girl, a man and three women with a rifle on Sept. 23 at a Macy’s makeup counter in the Cascade Mall in Burlington, Washington, 65 miles north of Seattle. Detectives said surveillance video showed it only took Cetin about a minute to shoot all five victims. After the shooting, documents said, he left his Ruger rifle with a 25-round magazine on top of a cosmetics counter, then fled the mall in a car. Cetin confessed to the shooting to detectives but did not explain why he did it.

Cetin had been charged with aggravated murder, which can bring the death penalty, but he had not entered pleas pending mental evaluations

He had attempted suicide by swallowing medication in November 2015, and he was involuntarily committed at Fairfax Hospital, an inpatient psychiatric facility in Kirkland, Washington, according to court records obtained by the Seattle Times. At the time, Cetin was ranked as at risk for serious self-harm.

He was diagnosed with disruptive disorder, depression, anxiety and attention deficit/hyperactivity disorder. Doctors prescribed medication, and he also was undergoing court-ordered mental-health counseling in the months before the shootings, the Seattle Times reported.

Cetin was a legal permanent resident of the U.S. who immigrated to this county as a young child from Adana, Turkey. He graduated in 2015 from high school in Oak Harbor, a rural community in western Washington state about 30 miles from the mall where he was accused of opening fire.

Friends and neighbors described Cetin as a young man who had gotten in trouble with the law several times, with three assault charges since 2015, The Washington Post reported. Several of Cetin’s former classmates described him as a socially awkward teenager who later was given to inappropriately touching female students.

After learning of Cetin’s death, the family of victim Chuck Eagan, a Boeing maintenance worker shot trying to protect his wife, said in a statement to the Skagit Valley Herald they were shocked.

“We pray that the man repented to God before his death,” the statement said. “While this event puts to rest our fear of his release, we harbor no ill will towards Mr. Cetin or his family and pray for their comfort as we know all too well the pain of grief.”