The shooter who killed at least 50 people at a gay nightclub in Orlando has been identified as Omar Mateen, law enforcement sources told The Post.

Mateen was a U.S. citizen with no apparent criminal history, was born to Afghan parents in New York in 1986 and was living in Port St. Lucie, Fla., according to multiple media reports.

Mateen had committed himself to ISIS before carrying out the bloodiest mass murder in US history at a gay nightclub in Orlando on Sunday, federal officials said.

Mateen “made a pledge of allegiance to ISIS,” California Rep. Adam Schiff, the top Democrat on the House Permanent Select Committee on Intelligence, told CNN.

Schiff said the timing and target of the attack can’t be a coincidence.

“The fact that this shooting took place during Ramadan and that ISIS leadership in Raqqa has been urging attacks during this time, that the target was an LGBT nightclub during (LGBT) Pride (month) and, if accurate, that according to local law enforcement the shooter declared his allegiance to ISIS, indicates an ISIS-inspired act of terrorism,” Schiff said.

“Whether this attack was also ISIS-directed remains to be determined. I’m confident that we will know much more in the coming hours and days.”

Meanwhile, US Sen. Bill Nelson (D-Fla.) cited intelligence sources as saying that there “appears to be” a link to Islamic radicalism and ISIS.

“I asked the FBI if there was any connection to Islamic radicalism. There appears to be,” Nelson said. “But they are naturally cautious and waiting throughout to see if if this is, facts emerge.”

“At this point, this is an incident, as I can see it, we can certainly classify as a domestic terror incident,” Jerry Demings of the Orange County Sheriff’s Office said.

The shooting — one of the worst mass shootings in US history — left at least 50 people dead, including the gunman, and more than 53 wounded, officials said.

Mateen was licensed to work as an armed security guard in the state of Florida, federal law enforcement sources said.

A source briefed on the matter told The Post that Mateen utilized ISIS-like tactics, automatic weapons and an explosive vest, though it was inoperable.

With Post wire services and additional reporting by David K. Li