A man armed with an assault rifle killed 50 people during a gay pride celebration at a nightclub in Orlando, Florida, early on Sunday in the deadliest mass shooting in U.S. history, a rampage President Barack Obama denounced as an act of terror and hate.
Police killed the gunman, who was identified as Omar Mateen, 29, a New York-born Florida resident and U.S. citizen who was the son of immigrants from Afghanistan and had twice been questioned by FBI agents in recent years.
Law enforcement officials were probing evidence suggesting the attack may have been inspired by Islamic State militants, although they said 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 Pulse nightclub in the heart of a city that is one of the most popular U.S. tourist destinations as some 350 patrons were attending a Latin music event in conjunction with gay pride week celebrations. Clubgoers described scenes of terror and pandemonium, with one man who escaped saying he hid under a car and bandaged a wounded stranger with his shirt.
"Words cannot and will not describe the feeling of that," 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 ranked as the deadliest single U.S. mass shooting incident, eclipsing the massacre of 32 people at Virginia Tech University in 2007.
"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."
U.S. officials cautioned, however, they had no conclusive evidence of any direct connection with any 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 U.S. counterterrorism official. "This guy appears to have been pretty screwed up without any help from anybody."
Still, the shooting was nearly certain to reignite emotional debates over American gun laws and homeland security in the midst of a U.S. presidential race shaping up to be a vitriolic campaign between Democrat Hillary Clinton and Republican Donald Trump.
The attack came six months after a married couple in California - a U.S.-born son of Pakistani immigrants and a Pakistani-born woman he married in Saudi Arabia, fatally shot 14 people in San Bernardino in an attack inspired by Islamic State. That couple died in a shootout with police hours after their attack on a holiday party attended by the husband's co-workers.