ISIS claims responsibility, Gunman had reportedly pledged allegiance

Multiple news outlets are reporting that the man who killed 50 people at a gay nightclub in Orlando called 911 shortly before the attack and pledged allegiance to the Islamic State.

The media outlets cited unnamed law enforcement officials in their reports.

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Danny Banks is an agent with the Florida Department of Law Enforcement. He says authorities are investigating whether the deadliest mass shooting in modern American history was an act of domestic or international terrorism, and if the shooter acted alone.

Also, ISIS claimed responsibility for the attack Sunday afternoon via its Amaq news agency, Reuters reported. It was not clear, however, if the shooting was actually directed by the terror group or only inspired by it.

The attack in Orlando at Pulse, which bills itself as "the hottest gay bar" in the city and was packed with more than 300 people for "Latin Night," was reported minutes after 2 a.m. Sunday. In addition to those killed inside the club, at least 53 people were taken to area hospitals.

Dozens of partygoers remained hostage in the club for several hours after the initial shooting, prompting SWAT teams to rush inside. Shortly after 6 a.m. local time, Orlando police tweeted that the gunman had been killed. Authorities said there was not believed to be any further threat to the area.

Click here for more details on the ISIS connection from Fox News.

The suspect in the Orlando attack was identified as Omar Mateen of Port St. Lucie, Florida. The gunman's father recalled to NBC News that his son recently got angry when he saw two men kissing in Miami and said that might be related to the assault.