ORLANDO, Fla. – The mayor of Orlando said 50 people killed in a mass shooting at a nightclub.

The Orlando nightclub terror shooter has been identified as Omar Saddiqui Mateen, two law enforcement officials tell CNN. The suspect is from Fort Pierce, Florida, officials say.

Approximately 50 people are dead inside Pulse nightclub, Orlando Police Chief John Mina said Sunday morning, just hours after a shooter opened fire in the club. At least 53 people have been transported for medical treatment, he said.

Police have shot and killed the gunman, Mina told reporters.

“It’s appears he was organized and well-prepared,” the chief said, adding that he had an assault-type weapon and a handgun. Orlando authorities said they consider the violence an act of domestic terror. The FBI is involved.

The shooting began around 2 a.m., and an officer responded, Mina said. The officer engaged in a shoot out outside the club. The gunman then ran into the club.

“That turned into a hostage situation,” Mina said. Authorities were getting calls from people inside the club but away from the gunman, the chief said.

More police rushed to the scene and broke down a door with an armored vehicle. At that point police shot and killed the gunman, Mina said.

CNN affiliate WKMG video captured club goers carrying injured people from the club.

“It’s just shocking,” said Christopher Hansen who was inside Pulse. He heard gunshots, “just one after another after another.”

“It could have lasted a whole song,” he said.

“Everyone get out of Pulse and keep running,” the nightclub posted on its Facebook page shortly after the violence began.

Orlando police warned residents to stay away from the area, and urged people not to call their offices. They declined to provide the number of casualties, saying details will be available later. Bomb sniffing dogs are on the scene.

‘Just bang, bang, bang!’

Pulse describes itself as “the hottest gay bar” in the heart of Orlando.

Hours before the shooting, the club urged partygoers to attend its “Latin flavor” event Saturday night.

Jovial, well-dressed crowds heeded the call in an event that turned into a nightmare.

“It was just, bang, bang, bang!” partygoer Christopher Hansen said of the gunfire.

Ricardo Negron Almodovar said he was in the club when the shooting started about 2 a.m. He barely escaped.

“People on the dance floor and bar got down on the floor and some of us who were near the bar and back exit managed to go out through the outdoor area and just ran,” he posted on the club’s Facebook page.

“I am safely home and hoping everyone gets home safely as well.”

Anthony Torres, who was at the club with friends, said he heard shots as he hurriedly drove off.

“The shots did not sound like a regular handgun, it sounded like it was shooting repetitively and it wouldn’t stop,” he said.

“So we knew what it was and we left there pretty quick. It was over 70 cop cars that were arriving there … It happened so quick that people got separated from each other.”

Tearful relatives waited outside the club as lights from police cars flashed in the background. Some implored the media to help them get word on their loved ones.

‘Just a lot of people screaming’

The sound of gunshots echoed beyond the club.

Jose Torres was clocking in to work at a Dunkin’ Donuts across the street when he heard them.

“It was something that I never heard before,” Torres said. “I had to run inside the store, and I saw just a lot of people screaming, crying. Just screaming and coming out running like crazy.”

Torres said he ducked into the Dunkin’ Donuts and called 911 as several people dashed out of the club, bleeding. Police and SWAT teams rushed to the scene.

“They don’t let nobody in or out,” he said. “The SWAT team is inside there.”

FBI agents were also assisting at the scene, agency spokeswoman Amy Pittman said.

Authorities have conducted a controlled explosion near the nightclub, according to Orlando police.

Tom Fuentes, a CNN law enforcement analyst, said controlled explosions are used to breach a door or when a subject is barricaded in a room and police want to use a stun grenade to temporarily freeze their central nervous system.