A gunman opened fire at a gay night club in Orlando, Florida, early Sunday, killing 50 people and wounding 53 more before he was killed in a shootout with SWAT team members. Here’s what we know about the deadliest mass shooting in U.S. history:

THE SHOOTER: Authorities have identified the shooter as 29-year-old Omar Mateen of Fort Pierce, Florida. In a 911 call from the club, Mateen professed allegiance to the leader of the Islamic State, Abu Bakr al-Baghdadi. Mateen was a U.S. citizen born in New York. His ex-wife said his family was from Afghanistan.

Authorities say Mateen was not under surveillance, but that in 2014, they discovered he had ties to an American suicide bomber. They said the ties were minimal and they didn’t think he represented a threat at the time.  

Mateen’s father, Seddique Mir Mateen, said his son got angry when he saw two men kissing in Miami a couple of months ago. He said that might be related to the attack. The father said the attack had nothing to do with religion.

FATHER’S ACTIVITIES: A former Afghan official says Seddique Mir Mateen appears on a television program known for “its anti-U.S. tirades” and “pro-Taliban” remarks. The official says the program is broadcast in the Dari language. The official spoke only on condition of anonymity because he did not want to be linked to coverage of the shooting.

\WHAT HAPPENED: Police say Mateen, equipped with an assault rifle and a handgun, opened fire on patrons early Sunday. He also exchanged fire with an officer working at the club about 2 a.m., when more than 300 people were inside. Police say the gunman then went back inside and took hostages. Police sent in a SWAT team to rescue hostages about 5 a.m. and Mateen died in an exchange of gunfire with SWAT officers.