Omar Mateen, who murdered 49 people at the Pulse nightclub in Orlando on Sunday, was a sophomore in Stuart, Florida when the terror attack unfolded.
Orlando gunman Omar Mateen jumped up and down and cheered as the Twin Towers fell on 9/11, former classmates have revealed.
Mateen, who slaughtered 49 people at the Pulse nightclub Sunday morning, was a sophomore in Stuart, Florida, when the terror attack unfolded in 2001.
Read: Orlando Shooter Had Visited Pulse Nightclub Several Times, Used Gay Chat Apps: Witnesses
One classmate told the Washington Post that after the attacks, Mateen seemed to make fun of how America was targeted.
“He was making plane noises on the bus, acting like he was running into a building,” Robert Zirkle told the newspaper. “After 9/11 happened, he started changing and acting different."
Another student reportedly remembered Mateen smiling and said he claimed Osama bin Laden was his uncle.
One of Mateen's former colleagues, Dan Gilroy, said he was also troubled by the gunman.
"I felt that he had the propensity for violence, absolutely," Gilroy told Inside Edition. "He spend most of the time complaining and railing and insulting and threatening to murder women and blacks."
Read: Hospitalized Victim Describes Orlando Attack: 'He Shot Everyone Who Was Dead on the Floor'
He said he also heard Mateen make derogatory comments about homosexual and Jewish people.
Officials say Mateen pledged allegiance to ISIS in a phone call to 911 during Sunday's attack, which left 49 dead and 53 injured.
Watch: See Inside Orlando Gunman's Suburban Florida Home
