A gunman wielding an assault-type rifle and a handgun opened fire inside a crowded Florida nightclub early Sunday before dying in a gunfight with SWAT officers, police said. The attack left about 50 people dead and more than 50 others wounded.

Authorities were investigating it as an act of terrorism.

The suspect exchanged gunfire with an officer working at the gay club known as Pulse Orlando around 2 a.m., when more than 300 people were inside. The gunman then went back inside and took hostages, Police Chief John Mina said.

Around 5 a.m., authorities sent in a SWAT team to rescue the hostages.

In addition to the guns, the shooter also had some sort of "suspicious device," Mina said.

Authorities were looking into whether the attack was an act of domestic or international terror, and if the shooter acted alone, according to Danny Banks, an agent with the Florida Department of Law Enforcement.

"This is an incident, as I see it, that we certainly classify as domestic terror incident," Orange County Sheriff Jerry Demings said.

FBI agent Ron Hopper said there was no further threat to Orlando or the surrounding area.

When asked if the gunman had a connection to radical Islamic terrorism, Hopper said authorities had "suggestions that individual has leanings towards that."

Several news organizations identified the gunman as Omar Mateen of Port St. Lucie, Florida.

Police had said previously on Twitter that there was a "controlled explosion" at the scene of the shooting. Mina said that noise was caused by a device intended to distract the shooter.

A woman who was outside the dance club early Sunday was trying to contact her 30-year-old son, Eddie, who texted her when the shooting happened and asked her to call police. He told her he ran into a bathroom with other club patrons to hide. He then texted her: "He's coming."

"The next text said: 'He has us, and he's in here with us,'" Mina Justice said. "That was the last conversation."

Dozens of police vehicles swarmed the area around the club. At least two police pickup trucks were seen taking what appeared to be shooting victims to the Orlando Regional Medical Center.

Pulse posted on its own Facebook page around 2 a.m.: "Everyone get out of pulse and keep running." Just before 6 a.m., the club posted an update: "As soon as we have any information, we will update everyone. Please keep everyone in your prayers as we work through this tragic event. Thank you for your thoughts and love."

Local, state and federal agencies were investigating. (Associated Press)

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