Friends and classmates say the 21-year-old suspect in the Boulder, Colorado, shooting was a tormented wrestler with a short fuse

• Police identified Ahmad Alissa, 21, as the suspect in the mass shooting in Boulder, Colorado.
• Alissa is accused of gunning down 10 people at a King Soopers market on Monday.
• Some who knew Alissa in school remember him for his temper. Another said he was a "normal" kid.

Ahmad Al Aliwi Alissa, whom police identified as the suspect in the mass shooting at a King Soopers grocery store in Boulder, Colorado, on Monday, lived most of his life in suburban Colorado and had a temper, those who know him told reporters.

Alissa, 21, was injured in the shooting and is in stable condition, the police said. He has been charged with 10 counts of murder and is scheduled to appear in court on Thursday.

The victims in the shooting have been identified as Denny Stong, 20; Neven Stanisic, 23; Rikki Olds, 25; Tralona Bartkowiak, 49; Suzanne Fountain, 59; Teri Leiker, 51; Eric Talley, 51, a police officer; Kevin Mahoney, 61; Lynn Murray, 62; and Jody Waters, 65.

"We are going to do everything in our power to make sure this suspect has a thorough trial," Boulder Police Chief Maris Herold said on Tuesday..

Authorities said the police had not yet identified a motive. Court documents viewed by Insider said Alissa had purchased a rifle six days before the shooting.

In an affidavit for an arrest warrant reviewed by Insider, Detective Sarah Cantu wrote that Alissa had removed all his clothing and was dressed only in shorts when he was arrested outside the market. He had blood on his right thigh, Cantu said.

Alissa lives in Arvada, a city 30 minutes south of Boulder.

During the investigation into the shooting, a woman who recently married Alissa's older brother told the police she had seen him in the family's home a few days earlier playing with a weapon she described as a "machine gun," the affidavit said.

Investigators learned that Alissa had purchased a Ruger AR-556 pistol on March 16, the affidavit said.

A temper and paranoia

Alissa's family immigrated to the US from Syria in 2002, when he was a toddler. His parents eventually opened a restaurant, Sultan Grill, in Arvada, according to Colorado business records.

Alissa's brother, Ali Aliwi Alissa, told The Daily Beast that Ahmad had acted paranoid and that it got worse when he started high school.

"The guy used to get bullied a lot in high school, he was like an outgoing kid but after he went to high school and got bullied a lot, he started becoming anti-social," Ali Alissa told The Daily Beast. Ali Alissa added that he believed the shooting was "not at all a political statement" but the result of "mental illness."

Ali Alissa also told CNN said that his brother acted paranoid after 2014.

"He would say, 'Someone is chasing me, someone is investigating me,'" Ali Alissa told CNN. "And we're like, 'Come on man. There's nothing.' ... He was just closing into himself."

It was not clear whether Alissa had been diagnosed with a mental illness, and authorities have not disclosed a motive. Researchers have long said that mental illness is not an indicator of violence; people with mental illnesses are more likely to be victims of violence than perpetrate it.

A man identifying himself as Alissa's brother-in-law told The Sun he was "strange," calling him a "loner" who would sit away from everyone during family dinners. Insider was not able to independently confirm the man's relation to Alissa.

"He has a reputation for being stupid, not smart," Usame Almusa told the outlet. "He was not like a proper Muslim, I don't know what kind of Muslim he was. He did not go to the mosque I go to."

Almusa added that Alissa lived in his parents' basement and worked at the family's restaurant, The Sun reported.

A history of violence

Alissa was a wrestler at Arvada West High School and had shared photos of himself in his uniform on social media. Facebook has since deleted his accounts there and on Instagram.

Those who wrestled with Alissa in high school described him as having a temper. A police report from November 2017 said he had attacked a classmate, leaving him "bleeding from the nose," "crying and throwing up," and afraid to return to school.

Alissa said at the time that the classmate had been bullying him for a year and had called him names like "terrorist," the report said. The school's resource officer wrote in the report that there had been no allegations of bullying from Alissa.

Witnesses said it looked random. Alissa later pleaded guilty to assault and was sentenced to two months of probation and 48 hours of community service.

A short fuse

Damien Cruz, who was friends with Alissa and his older brother in high school, told Insider that the two of them bonded over video games and would hang out together after school.

Alissa kept to himself a lot of the time but was also approachable, he said. They'd talk mostly about video games and high school.

Cruz remembered that Alissa had a tendency to lash out when he lost wrestling matches.

Racism was also prevalent at their high school, Cruz said.

"But he wasn't the guy to bully people, and he didn't start any drama," Cruz told Insider. "The bullying and drama just found him, and when it did he reacted over the top."

A former wrestling teammate, named Dayton Marvel, told The Denver Post that Alissa was "kind of scary to be around" and once had an outburst during an intra-team match where he threatened to kill people."

Marvel added that Alissa was especially sensitive about his faith, saying: "He would talk about him being Muslim and how if anybody tried anything, he would file a hate crime and say they were making it up."

Former classmates are surprised

Another teammate of Alissa's identified only as Conrad told The Daily Beast that he was surprised by the news but also remembered Alissa's hotheaded behavior.

"One thing I can tell you is he didn't take losing very well," the man said. "I remember that in wrestling. He would throw his headgear, wouldn't talk to the coaches when he lost. If I remember correctly, even cussed out one of the coaches one time."

Mark Dorokhov, who studied at Arvada West for a few months in 2017, told Insider that he sat with Alissa at lunch and that he'd always seemed like a "normal" kid.

"Me being the new kid, I guess, he came up to me," he said. "We talked for a minute, and we started to go to lunch together for a bit."

Dorokhov, now 22, remembered that Alissa played sports and wrestled after school and had a few other friends who sat with them at lunch. Dorokhov said Alissa never seemed angry during the time they knew each other.

"It's very disappointing," Dorokhov said, adding that they didn't stay in contact when he left the school.

When Dorokhov saw Alissa's mugshot, he didn't even recognize the teen he had sat next to in high school.

"It looks like an old dude," he said.