An Isil gunman armed with an assault rifle killed 50 people and injured a further 53 on Sunday at a gay nightclub in Florida in America’s worst ever mass shooting.
The homophobic rampage was condemned by president Barack Obama as an act of terror and hate.
Gunman Omar Mateen, 27, an Florida resident of Afghan descent was shot and killed by police in a firefight that quickly ensued after the massacre.
FBI officials say he pledged allegiance to the Islamic State in Iraq and the Levant (Isil) in a 911 call made shortly before the attack.
They also admitted they had been aware of Mateen as a possible home-grown terrorist in 2013 but had closed his case after a series of “inconclusive” interviews.
Shots rang out at the crowded Pulse nightclub in the heart of Orlando, about 15 miles northeast of the Walt Disney World Resort, as some 350 patrons were attending a Latin music event in conjunction with gay pride week celebrations. Clubgoers described scenes of carnage 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 US 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,” Mr 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, they had no conclusive evidence of any direct connection with foreign extremists.
“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 precise sequence of events in Orlando remained murky. But authorities said the gunman burst into the club and opened fire at about 2am, then took dozens of hostages that he held at gunpoint inside a bathroom during a three-hour siege that ended when police stormed the building using armoured cars and killed the gunman.
Officials in Orlando, a city of 270,000 people, were visibly shocked at the high death toll.
“We’re dealing with something that we never imagined and is unimaginable,” Orlando mayor Buddy Dyer said. He said 39 people died inside the club, two outside, and nine others died after being rushed to the hospital.
Mateen had twice been interviewed by FBI agents, in 2013 and 2014, after making comments to co-workers indicating he supported militant groups, but neither interview led to evidence of criminal activity, the FBI’s Hopper said.
Mr Hopper said Mateen was questioned in 2014 about his contacts with Moner Mohammad Abu-Salha, a US citizen who also had lived in Florida and became a suicide bomber in Syria that year.
Sunday night, federal agents combed through Mateen’s apartment in the Atlantic coast town of Fort Pierce, about 120 miles southeast of Orlando, searching for clues, as numerous evidence vans sat parked outside.
“The FBI is currently in the apartment. They’ll probably be there through the night,” said St Lucie County sheriff Ken Mascara.
Near Boulder, Colorado, Mateen’s former wife, Sitora Yusufiy, told reporters he worked for a time as a correctional officer at a juvenile detention center in Fort Pierce, and had once sought admission to a police academy.
She said she had been beaten by Mateen during outbursts of temper in which he would “express hatred towards everything.” Eventually, she was “rescued” from Mateen by members of her family who intervened four months into a stormy marriage that ultimately ended in divorce, she said.
“I know he had a history of steroids,” Yusufiy told reporters outside a home where she was staying with a man she identified as her current fiancee. She also described Mateen as “emotionally unstable,” “mentally ill” and bipolar.
Deborah Sherman, an FBI spokeswoman in Denver, confirmed that federal agents had interviewed Yusufiy in Colorado.
The imam of the Florida mosque where Mateen attended prayers for nearly 10 years said there were rumours that he was very aggressive, but that he was unusually quiet at the mosque and did not appear to have a single close friend in the community.
Within hours of the shooting, the presumptive presidential nominees of both major political parties weighed in with statements on the tragedy.
Donald Trump, who has called for a temporary ban on Muslims entering the United States, said he was “right on radical Islamic terrorism” and called on Mr Obama to resign for not using the words “radical Islam” in his statement folowing to the shooting.
Hillary Clinton echoed the president’s comments calling the attack both an act of terror and a hate crime, adding that the massacre “reminds us once more that weapons of war have no place on our streets.”