ORLANDO, Fla. - A man armed with an assault rifle killed 50 people at a packed gay nightclub in Orlando, Florida, on Sunday in the worst mass shooting in US history, which President Barack Obama described as an act of terror and hate.
Police killed the shooter, who was identified as Omar Mateen, 29, a Florida resident and US citizen who was the son of immigrants from Afghanistan.
Law enforcement officials were probing evidence that suggested the attack may have been inspired by Islamic State militants, although they cautioned there was no proof that Mateen had worked directly with the group.
"It has been reported that Mateen made calls to 911 this morning in which he stated his allegiance to the leader of the Islamic State," said Ronald Hopper, the FBI's assistant special agent in charge on the case.
Shots rang out at the crowded nightclub, in the heart of one the United States' most popular tourist destination cities, as some 350 people had packed in during celebrations of gay pride week. Clubgoers described scenes of terror, with one man who escaped saying he hid under a car and bandaged a wounded stranger.
"Words cannot and will not describe the feeling of that," clubgoer Joshua McGill said in a posting on Facebook. "Being covered in blood. Trying to save a guy's life."
Fifty-three people were wounded in the rampage. It was the deadliest single US mass shooting incident, eclipsing the 2007 massacre of 32 people at Virginia Tech university.
"We know enough to say this was an act of terror, an act of hate," Obama said in a speech from the White House. "As Americans, we are united in grief, in outrage and in resolve to defend our people."
US officials cautioned, however, that they had no conclusive evidence of any direct connection with Islamic State or any other foreign extremist group.
"So far as we know at this time, his first direct contact was a pledge of bayat (loyalty) he made during the massacre," said a US counterterrorism official. "This guy appears to have been pretty screwed up without any help from anybody."
The attack came six months after a married couple in California fatally shot 14 people in San Bernardino in an attack inspired by Islamic State.