Worst Mass Shooting in U.S. History: 49 Dead, 53 Injured at Gay Club

For the second time in two days, a shooting has rocked Orlando, Florida, but the incident that occurred around 2 a.m. Sunday morning is being linked to terrorism — ISIS has taken credit for the heinous act.

Officials say that 29-year-old Omar Mateen, a U.S.-born resident of Port St. Lucie, Florida, whose parents immigrated decades ago from Afghanistan, exchanged gunfire with a security guard at the popular gay hot spot Pulse in Orlando. He then made his way into the bar and fired off dozens of rounds, armed with an assault-style rifle, a handgun, and an explosive device.

The shooter held some patrons hostage before the police stormed the club, killing him.

Patrons describe a chaotic, bloody scene, and the death toll of 49. At least another 53 were injured. Multiple, nonstop gunshots can be heard in a Snapchat video taken at the scene, along with a witness exclaiming, "Oh, my God — people are getting shot, dude. Oh, my God, dude."

The FBI has indicated that Mateen may have had leanings toward radical Islam, but in a phone interview with NBC News, Mateen's father claimed the attack had "nothing to do with religion" and was instead tied to Mateen's homophobic disgust at seeing two men kiss in public recently.

"We were in Downtown Miami, Bayside, people were playing music. And he saw two men kissing each other in front of his wife and kid and he got very angry," Mir Seddique, Mateen's father, said in the call. "They were kissing each other and touching each other and he said, 'Look at that. In front of my son they are doing that.' And then we were in the men's bathroom and men were kissing each other. We are saying we are apologizing for the whole incident. We weren't aware of any action he is taking. We are in shock like the whole country."

In spite of Seddique's denial of his son's motivation, TMZ reports that Mateen is a known Islamic radical. Whether Mateen acted alone or was directed by a terrorist organization is not known, but authorities believe he specifically targeted a gay venue, and ISIS has issued a statement claiming responsibility for the attack, saying, "a solider of the Islamic State has carried out the attack."