45 people shot in mass shooting at nightclub in Orlando

At least 45 people were shot and killed and 53 others were injured in a mass shooting at a nightclub in Orlando, Florida, early Sunday morning, according to the Orlando Police Department.

The shooting occurred at Pulse, a gay nightclub in downtown Orlando, at around 2 a.m. ET. The suspect, identified as Omar Mateen, 29, was killed in a shootout with police after a three-hour standoff.

The shooting is the deadliest mass shooting in U.S. history, surpassing the 2012 Sandy Hook Elementary School shooting in Newtown, Connecticut, in which 26 people were killed.

The motive for the shooting is still unknown, but Mateen had reportedly pledged allegiance to the Islamic State group on a 911 call before the attack.

President Barack Obama has condemned the shooting as an "act of terror" and has ordered an investigation into the incident.

The FBI is investigating the shooting as an act of terrorism.