A gunman opened fire and took several hostages at a gay dance club in Orlando, Florida on Sunday night, killing at least 50 people and injuring 53 others in the deadliest mass shooting in US history.
Details about the attack and the shooter are still emerging, but here's what we know so far:
-The gunman has been identified by authorities as Omar Siddiqui Mateen, 29, a US citizen who was living in Port St. Lucie, a Florida city about a two-hour drive from Orlando. Mateen was born to parents from Afghanistan. He was reportedly known to authorities, but was not the subject of any specific investigation.
-NBC News quoted unnamed law enforcement officials as saying Mateen called 911 moments before the attack to pledge allegiance to the leader of the Islamic State. Sources also told the news network that Mateen referenced the Tsarnaev brothers, who carried out the Boston Marathon bombings in 2013, at the scene of the attack. President Barack Obama said the FBI is investigating the incident as an act of terrorism.
-The Islamic State's Amaq news agency said on Sunday that the group was responsible for the shooting, but it's unclear if the group was in contact with Mateen or if he was inspired by them. "The armed attack that targeted a gay night club in the city of Orlando in the American state of Florida which left over 100 people dead or injured was carried out by an Islamic State fighter," Amaq said.
-Mateen's ex-wife told the Washington Post that he was abusive and mentally unstable. "He was not a stable person," she said, speaking to the paper on the condition of anonymity. "He beat me. He would just come home and start beating me up because the laundry wasn't finished or something like that." The couple married in 2009 but divorced in 2011. She said he worked as a guard at a facility for juvenile delinquents.
-Orlando Police Chief John Mina said at a news conference on Sunday that Mateen used a handgun and an AR-15 assault rifle. Congressman Peter King, Chairman of the House Committee on Homeland Security, said the suspect had "training on weapons," but would not elaborate further.
-The shooting occurred at Pulse Orlando, a popular gay dance club in downtown Orlando. Police say the attack started at around 2am after Mateen began shooting at a club security guard. He then went inside and opened fire on the crowd before taking multiple people hostage. At around 5am, authorities used an explosive device to distract Mateen, then used an armored vehicle to break through the wall of the nightclub. Mateen was killed in a shootout with police shortly before 6am. Police said around 30 people were rescued during the shootout.
-There were about 230 people inside the club, which was about to close down for the night when the shooting happened. Some people escaped through the back of the club and hid in the nightclub's bathroom.
-Ron Hopper, the FBI agent overseeing the agency's Tampa field division, said investigators are exploring all possible angles right now to determine a motive. "We do have suggestions that the individual may have leanings towards that, that particular ideology [extremism]," Hopper said, "But right now, we can't say definitively, so we're still running everything around."
-Imam Muhammad Musir, president of the American Islam and the Islamic Society of Central Florida, implored the media and public to withhold their judgement until more information is confirmed. "It's our worst nightmare," Musir said. "It's supposed to be a beautiful morning but this is a heartbreaking morning."
-Florida Governor Rick Scott has declared a state of emergency and said he will "devote every resource available to assist with the shooting." The city of Orlando has also declared a state of emergency.
-According to USA Today, the owners of Pulse opened the club to promote awareness about the area's LGBT community. The club regularly hosts LGBT-related educational events.
-The shooting comes less than a day after a gunman shot and killed Christina Grimmie, a singer from the television show "The Voice," at a concert in Orlando. Officials at the news conference said that the two incidents are not connected.
This is a developing story, please check back for updates.
Follow VICE News on Twitter: @VICENews