ORLANDO — A gunman who pledged allegiance to the Islamic State opened fire in a crowded gay nightclub here early Sunday in a shooting that left 50 dead and another 53 wounded. The gunman, identified as Omar Mateen, had been investigated twice by the FBI for possible connections to terrorism, the bureau said, but no ties could be confirmed.
Mateen, 29, a U.S. citizen whose parents were from Afghanistan, called 911 and talked about the Islamic State shortly before the massacre at the Pulse nightclub, the worst mass shooting in U.S. history, Ronald Hopper, an assistant agent in charge of the FBI's Tampa Division, said at a news conference. Other federal officials said more explicitly that he had declared allegiance to the group.
"The FBI first became aware of him in 2013 when he made inflammatory comments to co-workers alleging possible terrorist ties," but could not find any incriminating evidence, Hopper said.
In 2014, the bureau investigated Mateen again, for possible ties to Moner Mohammad Abusalha, an American who grew up in Florida but went to Syria to fight for an extremist group and detonated a suicide bomb. Hopper said the bureau concluded that the contact between the two men had been minimal, and that Mateen "did not constitute a substantive threat at that time."
The suspicions did not prevent Mateen, who lived in Fort Pierce, from working as a security guard, or from buying guns. The federal Bureau of Alcohol, Tobacco, Firearms and Explosives said Mateen legally bought a long gun and a pistol in the last week or two, though it was not clear whether those were the weapons used in the assault.
The gunman stormed the Pulse nightclub armed with an AR-15-style assault weapon and a handgun around 2 a.m., turning what had been a celebratory night of dancing to salsa and merengue music into a panicked scene of unimaginable slaughter, the floors slicked with blood, the dead and the injured piled atop one another.
A three-hour standoff followed the initial assault, with people inside effectively held hostage until about 5 a.m., when law enforcement agencies led by a SWAT team raided the club in force, using armored vehicles and explosives designed to disorient and distract.
Hours after the attack, the Islamic State claimed responsibility in a statement released over an encrypted phone app used by the group. It stated that the attack "was carried out by an Islamic State fighter," according to a transcript provided by the SITE Intelligence Group, which tracks jihadi propaganda.
But officials cautioned that even if Mateen, who court records show was born in New York and had been married and divorced, had been inspired by the group, there was no indication that it had trained or instructed him, or had any direct connection with him. The pair who killed 14 people in San Bernardino, Calif., in December also proclaimed allegiance to the Islamic State, but investigators do not believe they had any contact with the group.
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"The FBI is appropriately investigating this as an act of terror," President Barack Obama said from the White House. He said that the gunman clearly had been "filled with hatred" and that investigators were seeking to determine any ties to overseas terrorist groups.
"In the face of hate and violence, we will love one another," he said. "We will not give in to fear or turn against each other. Instead, we will stand united as Americans to protect our people and defend our nation, and to take action against those who threaten us."
As he had after previous mass shootings, the president said the shooting demonstrated again the need for what he called "common sense" gun measures.
"This massacre is therefore a further reminder of how easy it is for someone to get their hands on a weapon that lets them shoot people in a school or a house of worship or a movie theater or a nightclub," Obama said. "We have to decide if that's the kind of country we want to be. To actively do nothing is a decision as well."
The shooting was the worst terrorist attack on U.S. soil since Sept. 11, 2001, and the deadliest attack in the nation's history on a specifically gay gathering. The FBI set up a hotline for tips.