Orlando Shooter, Omar Mateen Worked For Global Security Firm

The man behind the worst mass shooting in U.S. history worked since 2007 as a security officer at one of the world’s largest private security companies, which said Sunday it was “deeply shocked” by the news.

“We are cooperating fully with all law enforcement authorities, including the FBI, as they conduct their investigations,” G4S Secure Solutions said in a statement. “Our thoughts and prayers remain with the victims of this unspeakable tragedy, and their friends and families.”

Omar Mateen, 29, killed 50 people and injured 53 others at a gay club in Orlando, Florida, early Sunday morning, according to authorities, CNN reports.