US law enforcement officials and former associates of the 21-year-old accused of killing 10 people at a Colorado supermarket have described him as someone prone to sudden rage who was suspended from high school for leaving a classmate bloodied.
Ahmad Al Aliwi Alissa was booked into jail on Tuesday on murder charges a day after the attack at a grocery store in Boulder. He is due to make a first court appearance on Thursday.
Alissa had bought an assault weapon on March 16, six days before the attack, according to an arrest affidavit.
Investigators have not established a motive, Boulder County District Attorney Michael Dougherty said. It was not immediately known where the suspect purchased the weapon.
Among the dead was Boulder police officer Eric Talley, 51, who was the first to arrive after responding to a call about shots fired and someone carrying a gun, police chief Maris Herold said.
A law enforcement official briefed on the shooting said the suspect's family told investigators they believed Alissa was suffering some type of mental illness, including delusions.
Relatives described times when Alissa told them people were following or chasing him, which they said may have contributed to the violence, said the official, who wished to remain anonymous.
Alissa's sister-in-law told detectives he had been playing around with a weapon she thought looked like a "machine gun" about two days earlier, according to an arrest affidavit.
When he was a high school senior in 2018, Alissa was found guilty of assaulting a fellow student in class after knocking him to the floor, then climbing on top of him and punching him in the head several times, according to a police affidavit.
Alissa "got up in classroom, walked over to the victim and 'cold cocked' him in the head", the affidavit read.
One of his former high school wrestling teammates, Angel Hernandez, said Alissa got enraged after losing a match in practice once, letting out a stream of invectives and yelling he would kill everyone. Hernandez said the coach kicked Alissa off the team for the outburst.
"He was one of those guys with a short fuse," Hernandez said. "Once he gets mad, it's like something takes over and it's not him. There is no stopping him at that point."
On Tuesday night about 100 people mourned at a makeshift memorial near the grocery that was adorned with wreaths, candles, banners reading "(hash)Boulderstrong" and 10 crosses with blue hearts and the victims' names. Therapy dogs were on hand to provide comfort.
The other dead were identified as Denny Stong, 20; Neven Stanisic, 23; Rikki Olds, 25; Tralona Bartkowiak, 49; Suzanne Fountain, 59; Teri Leiker, 51; Kevin Mahoney, 61; Lynn Murray, 62; and Jodi Waters, 65.
Monday's attack was the seventh mass killing this year in the US, following the March 16 shooting that left eight people dead at three Atlanta-area massage businesses, according to a database compiled by the AP, USA Today and Northeastern University.
In Washington, President Joe Biden called on Congress to tighten the nation's gun laws.