People at a memorial service on Monday, the day after the shooting at the gay nightclub Pulse in Orlando, Florida. Reuters/Carlo Allegri Some of Omar Mateen's former grade-school classmates are talking in a new report that gives a glimpse into the Orlando shooter's troubled life.

The Wall Street Journal interviewed dozens of people who knew Mateen throughout his life, including colleagues, classmates, and family members.

Those who knew him in school in Port St. Lucie, Florida, suggested that Mateen, who died in a shootout with the police on Sunday after killing 49 people at a gay nightclub in the worst mass shooting in US history, had a tendency for threats and violent outbursts.

He was disciplined at school 31 times from 1992 to 1999, The Journal reported. He was convicted of battery in juvenile court for after getting in a fight with a fellow student. And he was suspended for 48 days from 1999 to 2001.

He cheered in class after the September 11, 2001, terrorist attacks and claimed that Osama bin Laden was his uncle, prompting the school to call his father, according to The Journal's report.

"We joked that he'd become a terrorist," Robert Zirkle, who knew Mateen through school in 2001, told The Journal. "And then he did."

"He was a mean, troubled child," Billie Miller, another classmate, said. "Scary."

One of Mateen's former teachers, Kathleen Zurich, described him to The Journal as a bully who called other students "ugly" and "gay." But he also had a softer side, she said.

"That’s the scary part," she told The Journal. "There was a nice side of him that you can see, and yet he can be so nasty. Almost like a Dr. Jekyll and Hyde personality."

Read the full Wall Street Journal report here.