Omar Mateen was arrested for beating up a classmate and experimented with marijuana in high school, according to documents released Thursday by the state.
In his application to become a prison guard, Mateen acknowledged the drug use as a juvenile and a fight in May 2001 while in math class at Martin County High School.
The fight led to misdemeanor charges of battery and disrupting a school function. The latter count was dropped and a judge withheld adjudication for battery.
Misdemeanor juvenile records are not public in Florida, so it's unclear how Mateen pleaded in the case.
"I did not get handcuffed and I did not go to jail," he wrote in his application to the Department of Corrections in 2006. "It was an experience of me growing up and I learned a big lesson from it."
Mateen, 29, killed 49 people and injured dozens of others at the Orlando gay bar Pulse on Sunday morning.
In the records released Thursday, Mateen was applying to become a prison guard at Martin Correctional Institution.
He was hired into a training program, earning about $550 a week and doing many of the same jobs as corrections officers. At the same time, he was enrolled in criminal justice courses at nearby Indian River Community College.
He was dismissed after about six months on the job at the prison; the state will not say why. Documents indicate he was terminated for an administrative reason unrelated to misconduct.
His application includes more than half a dozen recommendations from friends and neighbors who praised Mateen's judgment, work ethic and willingness to "give a hand if needed."
Port St. Lucie Police Officer Steve J. Brown, who met Mateen at a local Gold's Gym, wrote a personal letter to the state urging his hire.
"I would sleep soundly at night," Brown wrote, "knowing that a person like Omar is protecting us (from) the element which resides behind your concrete and steel walls."