WASHINGTON, June 12 (Xinhua) -- About 20 people were killed and 42 others wounded early Sunday morning in a shooting incident at a gay nightclub in Orlando, Florida said local police.

The gunman was found dead inside the Pulse nightclub after a shootout with the police, according to Orlando Police Chief John Mina.

"It appeared he was organized and well-prepared," said Mina at a press conference, adding that the suspect had an assault-type weapon and a handgun.

FBI spokesman Danny Banks said at the press conference that the mass shooting was being investigated as an act of terrorism.

The shooting began around 2:00 a.m. local time (0600 GMT) inside the club and there once was a confrontation between the suspect and an officer working at the club outside the venue, according to local police.

Then the suspect went back into the club to continue shooting and took hostages.

About three hours after the shooting first broke out, police shot and killed the suspect during actions to rescue the hostages, said Mina.

The Pulse describes itself as "the hottest gay bar" in Orlando, according to its website.