ORLANDO, Fla., June 12 (UPI) -- Law enforcement officials said Omar Seddique Mateen, the suspected gunman who opened fire at an Orlando nightclub, killing 50 people, pledged allegiance to the Islamic State.
Orlando, Fla., Mayor Buddy Dyer said that at least 50 people were killed and 53 more were hospitalized, making Sunday's attack at the Pulse nightclub the deadliest shooting in U.S. history.
"It's absolutely terrible ... 50 victims in one location, one shooting. Absolutely one of the worst tragedies we've seen," Orlando Police Chief John Mina said.
Before Sunday, the worst mass shooting in U.S. history was when a gunman opened fire on the Virginia Tech campus in Blacksburg, Va., killing 32 people in 2007.
Dozens of people were taken hostage inside the nightclub between 2 a.m. and 5 a.m. on Sunday morning by a gunman carrying an assault rifle and a handgun.
Orlando police tweeted that the Bureau of Alcohol, Tobacco, Firearms and Explosives stated Mateen purchased the firearms legally in Florida within the past week.
In an afternoon press conference, FBI Assistant Special Agent in Charge Ronald Hopper told reporters his agency took the lead on the investigation and that the FBI had been aware of Mateen since 2013 when he made "inflammatory comments" to coworkers that "alleged possible terrorist ties."
"The FBI thoroughly investigated the matter, including interviews of witnesses, physical surveillance and records checks," he said.
Mateen was interviewed twice during this time, but Hopper said the investigation was closed after the FBI was "unable to verify the substance of his comments."
He was interviewed by the FBI again in 2014 for possible ties to American suicide bomber Moner Abu-Salha, but determined that their contact was "minimal" and "did not constitute a substantive relationship or a threat at that time."
Earlier in the day, Hopper said the FBI was considering multiple motives for the shooting.
"At this point in time we're just conducting a general investigation, period," Hopper told reporters. "We'll determine whether officially if its a hate crime, or a terrorism incident or even a violent crime once we have all the facts in place."
Florida Gov. Rick Scott declared a state of emergency for Orange County after the shooting.
"You just can't imagine this would happen to our community, our state or anywhere in our country," Scott told reporters. "For somebody to go in there and be an active shooter and take that number of lives and injure that many people is clearly an act of terror. "
Officers killed the gunman Mateen, in a series of shootouts in which one officer sustained a head injury after a bullet hit his helmet.
The officers involved in the shootout were relieved of their duty and will be investigated by the Florida department of law enforcement, in what Mina said was standard practice.
An explosion was reported in the area of the nightclub but police described it as "a controlled explosion by law enforcement."
Orlando police bomb squad arrived at the scene to search the area and remove any "devices" similar to the one worn by the gunman that may have been placed inside the club.
"Tonight, we had a crime that will have a lasting effect on our community," Orlando Mayor Buddy Dyer said in a news conference.
Dyer said said that he contacted the White House, which granted a request to waive Health Insurance Portability and Accountability Act -- or HIPPA law -- in order to allow hospitals to contact the families of the injured.
It's unclear why Pulse -- which describes itself as a gay nightclub -- was targeted in the attack.
Terry DeCarlo, director of the Gay, Lesbian, Bisexual, Transgender Community Center of Central Florida, told the Orlando Sentinel the community was shocked and angered.
"This just makes no sense," he said. "This was an attack on the LGBT community."
Pulse describes itself as "the hottest gay bar" in Orlando and and was planning a "Latin flavor" event Saturday night.
Co-owner Barbara Poma opened Pulse in 2004 in memory of her brother John, who died of AIDS in 1991.
Of the fatalities, 39 victims and Mateen were pronounced dead at the site and two bodies were found in the parking lot, Dyer said. Another eleven people were taken to hospitals and pronounced dead there, he said.
Forty-three of the injured were transported to Orlando Regional Medical Center, a hospital spokesperson said, with 26 operations being performed.
The city of Orlando released the names of the first eight fatalities: Edward Sotomayor Jr., 34; Stanley Almodovar III, 23; Luis Omar Ocasio-Capo, 20; Juan Ramon Guerrero, 22; Eric Ivan Ortiz-Rivera, 36; Peter O. Gonzalez-Cruz, 22; Luis S. Vielma, 22; and Kimberly Morris, 37.