Suspected Cascade Mall shooter and Oak Harbor resident Arcan Cetin was found dead in the Snohomish County jail Sunday night, according to authorities.

Cetin apparently hanged himself, according to the Skagit County Prosecutor’s Office.

The Snohomish County Sheriff’s Office reported that the 20-year-old was found unresponsive at about 6:50 p.m. Corrections personnel immediately began multiple life-saving techniques, including CPR, but the efforts were not successful.

The Snohomish County Sheriff’s Office Major Crimes Unit is investigating the incident. It was the first death in the jail since 2014.

Cetin was moved to the Snohomish County jail from Skagit County March 10 at the request of his attorneys, the Skagit County Prosecutor’s Office reported.

Cetin, an Oak Harbor High School graduate, was accused of shooting five strangers to death at the women’s Macy’s store at the Burlington Mall on Sept. 23, 2016.

Cetin allegedly walked into the store carrying his father’s Ruger 10-22 rifle and opened fire. The victims were Sarai Lara, 16; Beatrice Dotson, 95, and Belinda Galde, 64, mother and daughter; Chuck Eagan, 61; and Shayla Martin, 52.

Cetin allegedly confessed to the shooting, which was captured on store surveillance cameras.

The family of one of the victims, Chuck Eagan, released a statement through the Skagit County Prosecutor’s Office.

The family thanked those who responded to the tragedy, especially law enforcement and the Skagit County Prosecutor’s Office, as well as the community.

“We’re understandably in shock over this development,” the statement says. “Our heart goes out to Mr. Cetin’s family. We pray that the man repented to God before his death.

“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.”

Skagit County prosecutors charged Cetin in January with five counts of aggravated first-degree murder. Prosecutors hadn’t yet made a decision on whether to pursue the death penalty.

Cetin did not enter a plea on the murder charges because his attorneys raised an issue of competency, which is a question of whether he was able to assist in his own defense.

Cetin was evaluated at Western State Hospital, but his attorneys were also having him evaluating by their expert, according to Skagit County Chief Criminal Deputy Prosecutor Rosemary Kaholokula.

Cetin was scheduled to appear in court next week for a hearing on the competency issue.

Cetin would have been able to enter a plea after the competency issue was resolved. The prosecutor would then have 30 days to decide whether to seek the death penalty.

The defense has an opportunity during that period to submit evidence of any mitigating circumstances that may affect the decision, Kaholokula explained.

Court records in Island County misdemeanor cases showed that Cetin had a long history of mental health problems. He was involuntarily committed to a psychiatric hospital in November of 2015 after he tried to kill himself by overdosing on medication, the records show.

Cetin has been diagnosed with or was suspected of suffering from at least 13 different disorders, including post traumatic stress disorder, attention-deficit disorder, autism, depression, fetal alcohol syndrome, intermittent explosive disorder, disruptive disorder, and several substance-abuse disorders, according to mental-health records.

Documents filed in Island County District Court cases also outlined Cetin’s difficult life.

He was born in Turkey. He witnessed his mother being beaten by her father and brothers daily; he was also abused by the men, who even chased him with knives.

Cetin also suffered from an injury at birth that affected his ability to move an arm and caused one arm to be significantly shorter than the other. He was run over by a bus when he was 6 years old, which broke his pelvis and left him unable to walk for months.

He was extremely socially awkward, according to a statement his attorney wrote in a district court case.

Cetin’s prior criminal history consists of three cases, all of which are gross misdemeanor assaults.

In a case in October 2014, Cetin was upset that his girlfriend was moving away and broke items in his home. Cetin went looking for a gun after overhearing his stepfather tell dispatchers that it was in a bedroom; his stepfather grabbed him and pinned him against a wall until the police arrived.

In another case, Cetin was accused of assaulting two girls at Oak Harbor High School in May of 2015. He was accused of rubbing his feet up their legs and inner thighs during a math class.

Cetin was again arrested in June 2015 after he and his stepfather got into an argument over pot smoking. During the argument, Cetin kissed his stepfather on the lips and struck him in the face, the police reports state.

Cetin was arrested the day after the Cascade Mall shooting near his apartment in Oak Harbor.