We haven’t seen this confirmed by law enforcement sources yet, but Senator Bill Nelson of Florida said — to multiple networks — that Omar Mateen has been linked to “Islamic radicalism” and “ISIS”:

Now, how about some confirmation from the FBI?

Also of note, RedState is reporting that Rep. Adam Schiff, referencing local law enforcement sources, said on CNN that Mateen “made a pledge of allegiance to ISIL” and was heard “praying in a foreign language.” Schiff went on to reiterate that his information was “second hand” and not confirmed: