(ORLANDO, Fla.) -- New details of the horror that transpired inside of a gay nightclub in Orlando, Florida have started to emerge, as people across the country and around the world mourn the dead.
The shooting unfolded over the course of three hours early Sunday morning when a lone-wolf gunman, Omar Mateen, approached Pulse nightclub armed with a .223 caliber AR-type rifle and a Glock handgun. After engaging in gunfire with an officer stationed outside of the club, he entered and sprayed the venue with bullets. Forty-nine people are dead and more than 50 were injured in the shooting.
Mateen was also killed by police.
The shooter has been identified by officials as Omar Mateen of St. Lucie County, Florida, an American citizen with Afghan parents. After the shooting began, he called 911 to pledge his allegiance to ISIS, according to law enforcement officials. Mateen died in a gun battle with authorities after taking hostages.
The incident is the worst mass shooting in U.S. history and the deadliest terror attack on U.S. soil since the events of Sept. 11, 2001. Officials are investigating it as as a "domestic terror incident."
Orlando Chief of Police John Mina said in a press conference Monday morning that the demeanor of the killer was "cool and calm" while communicating with officers. He also acknowledged that Mateen "pledged an allegiance to ISIS."
At the same press conference, a spokesperson for the FBI said that the figure of 50 fatalities announced on Sunday had included the shooter among the dead. Forty-eight of the 49 bodies have been identified and 24 families have been notified by authorities.
Mateen was "on the radar" of U.S. officials for some time, but was not the target of a specific investigation, according to law enforcement officials.
Ties to the Islamic State?
ISIS supporters have cheered the massacre online and an ISIS communique referred to the shooter as an ISIS "fighter," but there’s no evidence that ISIS directed or had prior knowledge of the attack, terrorism observers told ABC News.
ISIS, which has strongholds in Syria and Iraq, has targeted gay men for beatings and murder in the Middle East, and has filmed its members throwing some men suspected of being gay from the roofs of buildings.
Mateen's father, Seddique, told ABC News his son was born in New York and grew up in St. Lucie County, Florida. Seddique said his son was a family man and a devout Muslim who never showed any signs of extremism, violence or hatred.
"I don't think he was radicalized," Seddique said. "That's what my gut feeling tells me."
LGBT Community Left Reeling
Community members held vigils Sunday evening, hours after the mass shooting took place.
From Orlando to Los Angeles and Atlanta; from the White House to New York's famed Stonewall Inn, a moment of silence was observed across the country at 6 p.m.
Blood Banks at Capacity
The outpouring of support and the urgent need for blood led hundreds to line up at the local OneBlood bank in Orlando, only for many to be turned away as the center reached capacity. But the local blood donation group urged donors to return in the coming days.
Aerial footage shot by ABC News' Orlando affiliate WFTV in Orlando also showed hundreds lined up down the block as people waited to donate blood.
Donations to the GoFundMe page for the victims of the nightclub shooting have surpassed $1 million and there is a new target goal of $2 million.
White House Reaction
President Obama delivered a somber statement midday Sunday, saying the Pulse massacre was "an act of terror and an act of hate." He also called Mateen "a person filled with hatred."
Obama also stressed the resilience of the people in the state.
"We're going to do everything we can to help bring the community together," he said.
Vice President Joe Biden also released a statement blasting the incident as "evil" and "abhorrent."
People from around the world showed their support by standing in solidarity with those affected by the Orlando nightclub shooting.
The Tel Aviv City Hall lit up with the American flag and a rainbow, the national symbol for gay pride.
Meanwhile, the Buckingham Palace released a statement offering condolences for the victims.
The Queen: "Prince Philip & I have been shocked by the events in Orlando. Our thoughts & prayers are with all those who have been affected"— The Royal Family (@RoyalFamily) June 12, 2016
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