UPDATED: In an act of domestic terrorism that ranks as the worst mass shooting in U.S. history, at least 50 people were killed and 53 others wounded after a gunman opened fire in a popular Orlando, Fla., nightclub early Sunday morning.

The gunman was identified as Omar Mateen, 29, a U.S. citizen born in 1986 to Afghan parents who lived in Port St. Lucie, about 130 miles south of Orlando. The gunman died at the scene in a shootout with police.

“We had a crime that will have a lasting effect on our community,” said Orlando Mayor Buddy Dyer at a press conference. “We need to stand strong. We need to be supportive of the victims and their families.”

Mateen’s father, Mir Seddique, said his son had been angered when he recently saw two men kissing in Miami.

“We are saying we are apologizing for the whole incident,” his father told NBC News. “We weren’t aware of any action he is taking. We are in shock like the whole country. This had nothing to do with religion.”

Mateen was said to have been known to law enforcement officials, but the FBI closed its 2013 and 2014 investigations into his activities when it did not find anything that warranted further investigation.

According to NBC News, Mateen had called 911 and pledged allegiance to the leader of ISIS just before the attacks.

The death toll from the Pulse shootings surpasses the previous high of 33 dead in 2007 when a gunman went on a rampage at Virginia Tech college. A mass shooting in San Bernardino, Calif. last December left 14 dead and 21 wounded, while the 2013 killings at Sandy Hook Elementary School in Newtown, Conn., left 28 people dead and one injured.

In November, a coordinated series of attacks in Paris, including slayings at the packed Bataclan nightclub during a performance by Eagles of Death Metal, left 130 people dead, jolting the world as a brazen act of terror.

The shooting in Orlando began at roughly 2 a.m. ET on Sunday at Pulse, a gay bar, before escalating into a hostage situation that lasted until around 5 a.m. when police entered the club.

Police shot and killed the gunman, who used an assault weapon, a handgun, and an unidentified device. As the shooting began, Pulse posted on its Facebook page, “Everyone get out of pulse and keep running.”

One Orlando police officer was shot during the exchange of gunfire but was likely saved from death by his helmet, officials said. Police said they were looking into reports that the gunman may have had radical Islamist beliefs.

“We do have suggestions that that individual may have leanings toward that particular ideology,” FBI Assistant Special Agent-in-Charge Ron Hopper told media outlets. “But right now we can’t say definitively, so we’re still running everything to ground.”

Authorities said that the shooting is not connected to the murder of Christina Grimmie, a former contestant on “The Voice,” who was shot Friday night after performing a concert in Orlando. It is an active, ongoing investigation, but officials say that this appears to be an isolated incident.

The scene outside the three hospitals where the Pulse shooting victims were taken was frenzied, as people crowded around looking for family and friends believed to have been in the nightclub on Saturday night.

An eye witness interviewed by CBS News said that the club had themed nights and Saturday was “Latino” night.

Police urged anyone who was at the club on Saturday or those with information about the shooting to come forward and assist the investigation.

Local officials also put out an urgent call for blood donations to help the 53 victims. Within hours, local media showed pictures of long lines outside of blood donation centers.

GLAAD issued a statement about the shooting later on Sunday: “Our hearts are broken for the victims and families of the horrific tragedy in Orlando,” said GLAAD president & CEO Sarah Kate Ellis. “This unimaginable atrocity has not only robbed countless people of their loved ones, it has also stolen a sense of safety within the LGBTQ community. As we mourn the victims of this unspeakable attack, we are also reminded that the work to end hate in all its forms must continue.”