FBI Director James Comey says the gunman in the Orlando nightclub attack that killed 49 people had "strong indications of radicalization" and was likely inspired by foreign terrorist organizations.
Comey told reporters Monday that Omar Mateen spoke with a 911 operator three times early Sunday morning. Mateen also pledged loyalty to the head of the Islamic State group on his last call, Comey said.
The FBI investigated Mateen for 10 months beginning in May 2013. Comey said investigators later introduced him to confidential sources, followed him and reviewed details of some of his communications.
The early Sunday attack marked the deadliest mass shooting in modern U.S. history. Mateen died in a gun battle with police.