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Orlando shooter worked for global security firm

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NEW YORK — 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.

G4S said that Mateen started working for it in September 2007 and that company screening and background checks “revealed nothing of concern.” Another screening in 2013 turned up “no findings.” Florida state records show he was a licensed security officer.

The company said it learned in 2013 that Mateen had been questioned by the FBI, “but that the inquiries were subsequently closed.”

“We were not made aware of any alleged connections between Mateen and terrorist activities, and were unaware of any further FBI investigations,” it said.

The FBI says it interviewed Mateen in 2013 and 2014. “Those interviews turned out to be inconclusive, so there was nothing to keep the investigation going,” FBI Assistant Special Agent in Charge Ronald Hopper told reporters.

Mateen worked at a gated retirement community in South Florida, according to G4S.

Based in Jupiter, Florida, G4S says it has operations in more than 100 countries. It provides security guards, technology and other services. Its customers span a range of industries including mining, finance and retail.

Mateen, who was shot and killed by police, claimed allegiance to ISIS in a phone call to authorities around the time he carried out the “organized and well-prepared” attack, Orlando Police Chief John Mina said.