Last Updated Jun 17, 2016 7:13 PM EDT
ORLANDO -- The Florida Department of Corrections said Friday that Orlando nightclub shooter Omar Mateen was "involuntarily dismissed" from a corrections officer training program in 2007 after six months in the academy.
The corrections department told CBS News Mateen started the program in October 2006 and was asked to leave in April 2007.
"He did not complete his academic program and was not certified as a correctional officer," the department said in a statement.
During those six months, Mateen was disciplined for sleeping in class and sleeping on the firearms range, according to corrections records obtained by CBS News. He also had unexplained absences and was late to class.
Another student reported Mateen had asked if he would tell anyone if Mateen brought a gun to school.
He was dismissed shortly after the mass shooting at Virginia Tech, which left 32 people dead. The shooting was referenced in a recommendation Mateen be let go from the program, with a supervisor saying Mateen's behavior "is at best extremely disturbing."
"Omar Mateen was not fit to serve as a member of the FDC team, as he was unable to meet the basic requirements of the correctional officer academy," the corrections department said.
On Sunday, Mateen shot and killed 49 people and wounded another 53 before he was killed in a shootout with police at the Pulse nightclub, a gay bar in Orlando. Investigators say it was an act of terrorism and a hate crime.
The FBI continues to dig into Mateen's background. What they are uncovering is the 29-year-old's erratic behavior.
The St. Lucie County Sheriff's Office has confirmed that it wanted Mateen transferred out of a Florida courthouse in 2013 after they said he made inflammatory remarks about women and Jews and then praised the Fort Hood shooter.
Mateen's school records paint a picture of a troublesome, angry and inappropriate young boy, who struggled both academically and behaviorally.
The records show that he talked frequently about sex and violence as early as the third grade and was suspended for a total of 48 days during middle and high school.
When he was in 5th grade, a teacher at Mariposa Elementary School wrote of Mateen's inability to stay focused, his "lack of remorse," and his oppositional behavior.
High school classmate Robert Zirkle remembers being on a school bus with Mateen on September 11th.
"When he came up the stairs, he was acting like a plane, like had his arms out, he was making a plane noise," Zirkle told CBS News. "And he would -- he made like a boom sound or an explosion type sound, fell in his seat and was like laughing about it -- like it was a joke or something. And he did that a few times more on the bus, like when the bus would go, he would start doing it again, and when we would stop, he would make a boom again."
Investigators continue to look into Mateen's wife, who they say was with him on surveillance trips to the nightclub and Disney World.
Law enforcement sources told CBS News the couple exchanged text messages during the shooting. Authorities say it is likely she will face some charges.
'You have to go back and find out where she has been, how often she was with her husband, and what they were doing," former U.S. Attorney Vincent Cohen told CBS News. "When you put those two together, the knowledge and the possible act, then you have the possible charges."
Investigators have not found evidence that the Mateen was directed by ISIS, although he pledged allegiance to the group in a Facebook post just before the shooting and ISIS took credit for the attack.