Orlando shooter worked for major homeland security contractor

For nearly a decade before carrying out the shooting Sunday at the gay nightclub Pulse in Orlando, gunman Omar Mateen was employed by the global security firm G4S Secure Solutions. The firm — which Bloomberg reports was "consistently one of the biggest contractors with the U.S. federal government after the Sept. 11, 2001, terrorist attacks, mostly with the departments of Homeland Security and State" — hired Mateen in September 2007 as a security officer.

The role required that Mateen undergo "28 hours of classroom training by a licensed instructor," The Independent reports, and that he carry a weapon and obtain a license as a security guard from the state of Florida. "Mateen underwent company screening and background checks when he was recruited in 2007 and the check revealed nothing of concern,” G4S North America CEO John Kenning said in a statement. "His screening was repeated in 2013 with no findings. We were not made aware of any alleged connections between Mateen and terrorist activities."

However, while Mateen may have cleared the company's screenings, G4S reportedly was aware that Mateen had been interviewed by the FBI, though it said it was not aware the interviews concerned "alleged connections between Mateen and terrorist activities." In 2013, the FBI reportedly interviewed Mateen twice for "falsely claiming" that he had ties to the brothers who carried out the 2013 Boston Marathon bombing, The Guardian reports. Mateen's former coworker has claimed that Mateen talked openly about his FBI investigation, as well as his intense feelings of "anger and rage."

Most recently, Mateen was working as a security guard at a gated retirement community. The shooting at the Orlando nightclub early Sunday left 49 dead and 53 injured. Mateen was killed in a shootout with law enforcement.