Crime Everything We Know So Far About the Orlando Nightclub Shootings Get the latest information on the tragedy in Orlando By Stephanie Petit Stephanie Petit Stephanie Petit is a Royals Writer and Reporter at PEOPLE. People Editorial Guidelines Published on June 13, 2016 08:30 AM Share Tweet Pin Email Photo: Joe Burbank/Orlando Sentinel/TNS via Getty At 2 a.m. on Sunday, a man armed with an assault rifle and a handgun opened fire inside a crowded gay club called Pulse in Orlando, Florida. At least 50 people were killed and 53 more were wounded in what is now the deadliest mass shooting in American history. As authorities continue to investigate, here’s a look at everything we know so far about the tragedy: The gunman took hostages before being killed by police When alleged gunman Omar Mateen opened fire, an officer working security off-duty at the club responded, “engaging in a gun battle with the suspect” outside before the suspect went back into the club and took about 30 people hostage, Orlando Police Chief John Mina said at a Sunday morning news conference. The gunman was killed at 4:15 a.m. local time in an exchange of gunfire with an Orlando SWAT team, as officers moved in to rescue the hostages. Hundreds of Orlando residents showed up to donate blood When health officials in Orlando announced that blood banks were being depleted treating the dozens of wounded, residents responded. Hundreds of people lined up outside donation centers to wait their turn to help replenish supplies of blood. “You want to do something to help,” blood donor Frank Tiffany told The Orlando Sentinel. “It’s hard to believe. You have to do something to help. You can’t stay home.” Gunman Omar Mateen, 29, was born in New York. Omar Saddiqui Mateen, who was born in New York and was not from Orlando, was confirmed as the gunman Sunday afternoon. Authorities held off on initially identifying the gunman as they waited to contact his next of kin. An FBI source tells PEOPLE that his parents are from Afghanistan and his father is a known Taliban supporter who has a YouTube show in which he called for the arrest of former Afghan President Hamid Karzai, among others. WATCH: People Reporter Shares His Experience Reporting From Scene and Being a Member of Community Where Orlando Mass Shooting Took Place The gunman’s ex-wife claims he was abusive Sitora Yusufiy, the shooter’s ex-wife, said during a press conference on Sunday that she believes that Mateen suffered from mental illness. After calling her ex “bi-polar,” Yusufiy said he was deeply disturbed and abused her physically during their four-month marriage. (She also added that she had not spoken to Mateen or his family in at least seven years.) The pair met online eight years ago, and Yusufiy moved to Florida to marry him. “He was mentally unstable and mentally ill and he was obviously disturbed, deeply,” she said. “That’s when I started worrying about my safety and he was abusing me physically very often and not allowing me to speak to my family and he kept me hostage from them. And I tried to see good in him even then, but my family was very tuned-in to what I was going through and decided to visit me and rescue me out of that situation. The gunman called 911 and pledge allegiance to ISIS The gunman first called 911 about 2:30 a.m. local time, approximately 30 minutes after opening fire at Orlando’s Pulse, a federal law enforcement official tells PEOPLE. On that call, he announced he was shooting up the club and claimed he was armed with explosives a claim which authorities have not confirmed and which they are “still exploring,” the official says. “The 911 operator, using reverse-call technology, called back the gunman and it was then that he pledged allegiance to [ISIS leader] Abu Bakr al-Baghdadi,” the federal official tells PEOPLE. The gunman “also mentioned the Tsarnaev brothers,” who orchestrated the Boston Marathon bombings of 2013, the official says. ISIS has claimed responsibility for the attack Authorities are looking into the shooter’s background for possible connections. “Agents in Afghanistan are looking at the shooter’s connections there,” an FBI source with knowledge of the investigation tells PEOPLE. “He has family there. This is not to say his family is connected to the shootings. This is the normal course of an investigation like this. We ask questions.” “The Islamic State [ISIS] called for attacks on the West during Ramadan,” the source continues. “In the wake of San Bernardino, we are very much mindful of how this can play out.” According to the Associated Press, Islamic State radio called the shooter “one of the soldiers of the caliphate in America.” Mateen was “on the radar” of the FBI The federal law-enforcement official tells PEOPLE of the shooter: “The FBI was aware of this guy before today. He was on their radar.” Mateen’s father told NBC News this morning the shooting “has nothing to do with religion,” and instead pointed toward his son’s recent anger at two men kissing as a possible cause. The FBI says agents investigated Mateen twice for comments he made about Islamic terrorism, but were unable to find evidence to arrested him. RELATED VIDEO: Families Wait to Hear Word of Loved Ones in the Orlando Mass Shooting President Barack Obama called the shooting ‘an act of terror and hate’ President Obama called the shooting, the deadliest in American history, a “horrific massacre of innocent people”. Obama confirmed that although it is early in the investigation, “We know enough to say this was an act of terror and an act of hate.” “What is clear is that [the shooter] was a person filled with hatred,” he added. Police are still working to identify victims and alert families Yesterday, Orlando Mayor Buddy Dyer tweeted that although the Pulse nightclub is still an active crime scene, “law enforcement is working the scene as efficiently and diligently as possible while being respectful to the remains of the deceased.” A website is being set up to identify victims after their families have been notified. As of Monday morning, 24 people have been listed. Mayor Dyer also asked that anyone who may know a possible victim call a hotline at 407-246-4357.