Omar Mateen. CREDIT: MySpace

A gunman slaughtered 50 people and injured 53 in a crowded gay nightclub in Orlando, Florida early on Sunday before being shot and killed by SWAT officers.

This attack has been called the deadliest mass shooting in American history.

The shooter was identified as Omar S. Mateen.

According to CNN, Mateen called 911 and pledged allegiance to Isis.

Authorities are investigating it as an act of terrorism.

The suspect exchanged fire with an officer working at the club, when more than 300 people were inside. The gunman then went back inside and took hostages, after which SWAT retrieved them.