What We Know About the Suspected Orlando Night Club Shooter

Omar Mateen, a U.S.-born citizen, has been identified as the suspect in Sunday's mass shooting that left at least 50 dead and more than 50 others wounded at the Pulse Nightclub, a gay nightclub in Orlando, Florida.

Mateen's parents were born in Afghanistan, and he was "on the radar" of U.S. officials for some time, but was not the target of a specific investigation, law enforcement officials told ABC News.

A police officer working at the club responded to shots fired at 2:02 a.m., and then exchanged fire with Mateen, according to police.

At approximately 5 a.m., the SWAT team made the decision to rescue the hostages, officials said.

Mateen was killed in a gunfight with those officers early this morning, officials said.

FBI assistant agent in charge of the agency's Tampa division, Ron Hopper, said this morning investigators were "looking at all angles right now" to find a motive.

"We do have suggestions that that individual may have leanings towards that, that particular ideology [Islamic extremism]. But right now we can't say definitively, so we're still running everything around," he said.