Two and a half years before he killed 49 people in a June 12 shooting attack at Orlando's Pulse nightclub, Omar Mateen told investigators he'd been teased and verbally abused by co-workers for being Muslim. That abuse, he said, led him to claim ties to mass killers and terrorist groups, connections he later told the FBI he'd made up. The FBI concluded Mateen was not a threat.

The new information about Mateen emerged in Sheriff's Office documents released this week in Florida's St. Lucie County. Mateen worked as a guard for a G4S Solutions, a company that provided security at the St. Lucie County courthouse. Eventually, Mateen's behavior led the Sheriff's office to ban him from work at the courthouse and the company reassigned him.

The documents quote from interviews first with the FBI and later with his supervisors at G4S Solutions, in which Mateen detailed a series of encounters with co-workers between 2011 and 2013. Mateen told investigators he felt Sheriff's deputies and co-workers at the courthouse didn't like him because he was Muslim and called him a terrorist. Some suggested he could be acting normally while planning an attack, like Nidal Hasan and the Tsarnaev brothers, the people responsible for the Ft. Hood shootings and the Boston Marathon bombings, respectively. When boxes were sent to the courthouse on one occasion, Mateen said a co-worker called him a terrorist, saying, "We have to be careful Omar might send us a bomb and he will get his 72 virgins."

Mateen told investigators, he responded to the abuse by boasting of his ties to terrorist groups. He told co-workers he was related to the Boston Marathon bombers and the Ft. Hood shooter, also that he knew those involved in the 2013 attack on a mall in Nairobi, Kenya. In later interviews with the FBI, Mateen said none of that was true. The documents include a signed statement from him that says, "The boasting I did it just to satisfy the gang of coworkers who ganged up against me. There is no fact to it. I'm 100% pure American."

St. Lucie's Sheriff's department says after a thorough investigation, the FBI concluded Mateen's boasts were empty. "We do not believe he is a terrorist," an investigator said. "I don't believe he will go postal or anything like that."

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