A former co-worker of the Orlando nightclub shooter said that Omar Mateen was "a very troubled person."
Daniel Gilroy used to work at a community security gate alongside Mateen, who was identified as the shooter who killed 50 people and injured 53 others at Orlando's Pulse nightclub early Sunday morning.
"[Mateen] had a lot of rage in him," Gilroy told ABC News.
"When I say that he was unstable or unhinged, I mean this is a man who would lose his temper for no reason. He would kick walls, slap desks. I’ve seen him throw the chair across the room one time," Gilroy said.
Gilroy said he purposefully lost contact with Mateen in March 2015 when he left the job.
"I didn't want to be around him anymore," Gilroy said. "I’m not surprised at what he did. I always knew he had something in him like that. And if I had to pick one person that would be capable of that, it would be him."
The shooting started just after 2 a.m. on Sunday at the popular gay nightclub. Mateen died in a firefight with police when they raided the club at about 5 a.m. Federal authorities determined that Mateen had recently purchased the two guns he used during the shooting.
Mateen's ex-wife, Sitora Yusufiy, also said that Mateen had a temper that could turn violent.
"He would be perfectly normal and happy, joking, laughing one minute. The next minute his temper ... his body would just [go] totally the opposite," Yusufiy, 27, told ABC News. "Anger, emotionally violent — and that later evolved into abuse, to beating."