Omar Mateen conducted one of the worst mass shootings in U.S. history at an LGBT nightclub in Orlando, Florida. These actions have turned the spotlight on his employer, G4S, with which Mateen was a security guard since September 2007. G4S is the largest private security firm in the world and conducts extensive background checks on all employees. The company confirmed it had conducted two of these tests on Mateen during his time there and that the check revealed nothing of concern. These checks were in addition to two instances in 2013 and 2014 when Mateen was investigated by the FBI. However, a lack of evidence meant charges could not be laid at either time. These investigations didn’t trigger any cause for concern at G4S either. “In 2013, we learned that Mateen had been questioned by the FBI but that the inquiries were subsequently closed,” John Kenning, the company’s regional CEO for America. We were not made aware of any alleged connections between Mateen and terrorist activities, and were unaware of any further FBI investigations.”