According to some former classmates of Orlando terrorist, Omar Mateen, he terrorized his Florida grade school - Mariposa Elementary by bullying students and threatening to go on a shooting spree in school. He constantly bullied others and once told a group of kids at their school he was going to bring a gun to school and kill everyone. When it became clear that he didn't sound like he was joking, they immediately told a teacher, and Mateen was suspended for 2 weeks.
According to his classmates who have granted interviews after the club massacre, his behavior issues continued into middle school and he also threw chairs and spat at teachers. He even bragged to his High School classmates on 9/11 about being related to Osama bin Laden. His former classmates insist the warning signs were there at an early age and wish more had been done in terms of discipline or counseling.