ORLANDO, FL (RNN) - A gunman who professed allegiance to the Islamic State carried out the worst shooting in U.S. history killing 50 and wounding 53 more in a shooting at a gay night club in Orlando, FL.
The shooter was identified at Omar Mateen, a U.S. citizen living in Port St. Lucie, FL. He was killed in a shootout with police after holding hostages in the club's bathroom.
Speaking from the White House briefing room, President Barack Obama said the shooter was "filled with hatred" but said the FBI had not reached any definitive conclusion about a motive.
"It is still early, but we know enough to say it was an act of terror and an act of hate," Obama said. "This is a sobering reminder that attacks on any American regardless of race, ethnicity, religion or sexual orientation is an attack on all of us. No act of hate or terror will change who we are or the values that make us Americans."
Shortly after speaking, the White House released a proclamation ordering all flags on federal property be lowered to half-staff.
The attack surpassed the shooting at Virginia Tech in 2007 where 32 people were killed at the deadliest in the country's history.
Rep. Adam Schiff (D-CA), the ranking Democrat on the House Intelligence Committee, said he was briefed by the Department of Homeland Security that Mateen had professed an allegiance to the Islamic State. FBI officials indicated he called 911 and referenced the bombing at the Boston Marathon in 2013.
CBS News confirmed Mateen worked as a security guard. However, police officials said his family members are not U.S. citizens.
Police are searching the gunman's home as well as social media for evidence. Mateen is suspected of carrying out a hostage situation in what officials are calling "domestic terrorism" and police and FBI are investigating if he had ties to any terrorist groups. The suspected gunman's father told several media outlets he suspected an anti-gay motivation rather than a religious one.
Police in Los Angeles arrested a man with weapons and explosives who said he was headed to the gay pride parade. Officials do not believe that incident was connected to the Orlando shooting.
Obama was briefed on the shooting and the White House released a statement saying he was in communication with the FBI. He is expected to speak on the shooting Sunday afternoon.
"The President was briefed this morning by Lisa Monaco, Assistant to the President for Homeland Security and Counterterrorism, on the tragic shooting in Orlando, Florida," the statement said. "Our thoughts and prayers are with the families and loved ones of the victims. The President asked to receive regular updates as the FBI, and other federal officials, work with the Orlando Police to gather more information, and directed that the federal government provide any assistance necessary to pursue the investigation and support the community."
Police responded to calls of a shooting at 2 a.m. Eastern and exchanged gunfire with a shooter inside Pulse, a gay night club. The gunman then took hostages and police entered the club about three hours later, exchanging more gunfire and killing the suspect.
Orlando Police Chief John Mina confirmed the shooter was carrying an assault style rifle, a handgun and a "suspicious device" with him. He said officers decided to rescue the hostages at 5 a.m. using an explosive device to enter through a wall in the club. At 5:45 a.m., police tweeted the suspect was dead.
Mina said about 30 people were rescued after police entered the building. One officer was injured in the crossfire, but was wearing a protective helmet that Mina said likely saved his life.
"Just to look into the eyes of our officer told the whole story," Mina said. "Some of those officers had 20-plus years on the force. You could tell they were shaken by this incident, by what they saw. They did an unbelievable job rescuing hostages this kind of tragedy takes a toll, even on law enforcement officers."
Orlando Mayor Buddy Dyer said the influx of patients to the hospitals created problems due to confidentiality regulations, which he worked to have waived for victims' families.
"The CEO of the hospital came to me and said they had an issue related to the families who came to the emergency room. Because of HIPAA regulations, they could not give them any information," Dyer said. "So I reached out to the White House to see if we could get the HIPAA regulations waived. The White House went through the appropriate channels to waive those so the hospital could communicate with the families who were there."
Muhammad Musri, with the Islamic Society of Central Florida appeared at a police press conference and urged caution in passing judgment without knowing the facts surrounding the suspect and his motivation.
"I caution media in rushing to judgment and sensationalizing the story," Musri said. "Don't want the story to be shifted from where it is. We are mourning, we are sad and it's not really time for sensational news and rushing to judgement. We should all wait until information, facts come out from investigators."
Police said the shooter was "organized and well-prepared" and Orange County Sheriff Jerry Demings called it a "domestic terrorism incident."
"We are a strong, resilient community," Dyer said. "We need to stand strong and we need to be supportive of the victims and their families."
Musri also urged people to feel compassion for the victims.
"I stand as a faith leader with the law enforcement community in this hour of horror that was brought upon our city," Musri said. "I call on fellow faith leaders, please pray for the victims and their families in this hour - this Sunday morning - it was supposed to be a beautiful morning, but it already a heart-breaking morning."
Dozens of vehicles including the Orlando Fire Department's bomb squad and hazardous material team arrived at the scene of the shooting, which occurred around 2 a.m.
Near the time of the shooting, the club posted on its Facebook page, "Everyone get out of Pulse and keep running."
After news of the shooting, family members and friends of people who were known to be in the club awaited word about injuries or possible deaths.
Chris Hansen managed to escape the club after shots rang out.
"It was just one after another, after another, after another. It could've lasted a whole song, because after everybody was out, shootings were still going and the cops were yelling, 'Go, go, clear the area, clear the area!'" Hansen said.
CNN reports three Orlando area hospitals have been placed on lockdown because of the mass shooting. There were reports of additional shots fired at a nearby hospital, but Mina said that claim was unfounded.
As day broke Sunday morning, buses arrived to transport those who had not been injured but were inside the club at the time. On Twitter, the police called calling for witnesses to go to police HQ.
Ricardo J. Negron Almodovar, commenting on Facebook, said he witnessed the incident.
"I was there. Shooter opened fire @ around 2:00 a.m. People on the dance floor and bar got down on the floor and some of use who were near the bar and back exit managed to go out through the outdoor area and just ran," Almodovar wrote.
The hashtag #prayfororlando, which emerged on Twitter after the fatal shooting of singer Christina Grimmie Friday night at the city's Plaza Live Theater, is once again trending on Twitter. Grimmie was killed after her concert at the venue by a 27-year-old man who later killed himself.
Mina said there was no indication the Pulse shooting was connected to Grimmie's murder.