Orlando gunman 'was regular at gay nightclub'
The FBI is investigating reports that Orlando gunman Omar Mateen was a regular at the gay nightclub where he killed 49 people in America's worst mass shooting.
A number of possible explanations and motives for the bloodbath have emerged, with Mateen having professed allegiance to the Islamic State group (IS), his ex-wife saying he was mentally ill, and others suggesting he was driven by a hatred of gays.
The picture grew more complex as patrons of the Pulse nightclub came forward to say that they had seen the 29-year-old American-born Muslim there a number of times, and that he had been using gay dating apps.
Mateen had a wife and a three-year-old son.
Jim Van Horn, 71, said Mateen was a regular at the club. "He was trying to pick up people. Men," he claimed.
While acknowledging he did not know Mateen well, Mr Van Horn said: "I think it's possible that he was trying to deal with his inner demons, of trying to get rid of his anger of homosexuality."
Wielding an AR-15 semi-automatic rifle and a handgun, Mateen opened fire at the club early on Sunday in a three-hour rampage and hostage siege which ended with a Swat team killing him.
It is the deadliest mass shooting in modern US history. During the attack, he called 911 to profess allegiance to IS.
Six of the more than 50 people injured in the atrocity are said to be critically ill, with five others in a "guarded" condition.
Dr Michael Cheatham, of the Orlando Regional Medical Centre, said at a hospital news conference that doctors recalled victims arriving in "truckloads" on the night of the rampage.
Dr Chadwick Smith described calling in additional staff members and telling them: "This is not a drill, this is not a joke." He said everyone answered: "I'll be right there."
US president Barack Obama will visit Orlando on Thursday to pay his respects to the victims and stand in solidarity with the community, the White House said.
Asked about reports that Mateen may have been in the club before, his father, Seddique Mateen, said from his home in Port St Lucie, Florida, that his son may have been "scouting the place".
Asked if his son was gay, the Afghan immigrant replied: "No."
He said that he was not aware of his son having any mental health problems and that he never saw any signs he had become radicalised.
If he had seen anything differently, he said, "I would have called law enforcement immediately".
The elder Mateen said that apart from one time his son got angry a few months ago over seeing two men kissing, he did not witness any anti-gay behaviour from him.
The White House and the FBI said Mateen appears to be a "homegrown" extremist who had expressed support not just for IS, but for other radical groups that are its enemies.
"So far, we see no indication that this was a plot directed from outside the United States, and we see no indication that he was part of any kind of network," FBI director James Comey said.
He added that Mateen was clearly "radicalised," at least in part via the internet.
Mr Comey said the FBI also was trying to determine whether Mateen had recently scouted Disney World as a potential target.
He defended the bureau's handling of Mateen during two previous investigations in 2013 and 2014 into possible terrorist ties. As for whether there was anything the FBI should have done differently, Mr Comey said: "So far, the honest answer is, I don't think so."
Mateen was added to a terror watchlist in 2013 when he was investigated, but was taken off it soon after the matter was closed, according to Mr Comey. People on that database are not automatically barred from buying guns. Mateen purchased his weapons in June, long after his removal from the list.
On Monday night, about a mile from Pulse in central Orlando, thousands gathered for a vigil to support the victims and survivors, with the names of the dead read aloud.
The event was held on the lawn of Orlando's main performing arts venue, where mourners created a memorial of flowers, candles and notes for the victims.