FBI 'highly confident' that Orlando shooter was 'radicalized'

The head of the Federal Bureau of Investigation said Monday agents were "highly confident" that Orlando shooter Omar Mateen was "radicalized," at least in part through information he found online.

James Comey said it was still not clear if Mateen was part of an established extremist network or which group may have inspired him, but he told reporters: "We'll leave no stones unturned and we'll work all day and all night to understand the path to that terrible night."

Forty-nine people were killed and 53 others wounded in the shooting rampage at a gay nightclub in Orlando in the early hours of Sunday. Mateen, who pledged allegiance to the Islamic State group during the attack, was killed in a shootout with police.