Orlando nightclub shooting: What we know

A heavily armed assailant opened fire in a gay Orlando nightclub early Sunday, killing 50 people in the deadliest shooting spree in U.S. history. Here is what we know so far:

• How it started: Orlando police said the tragedy began around 2 a.m. when three police officers engaged the suspect in a gunbattle outside the club. A hostage situation then took place inside, and a SWAT team was called in. Police received updates from trapped patrons and decided to storm the club at about 5 a.m. Police used an armored vehicle to break through a wall at the nightclub, then SWAT team members exchanged gunfire with the suspect. He was shot and killed.
• Victims: There were more than 300 people inside the club, police said. Some people escaped through the back. Police and Orlando city officials said 50 people were dead and another 53 people were hospitalized. It is unclear what the condition of the wounded are. 
• The suspect: Federal law enforcement officials told Paste BN the suspect had been identified as Omar Mateen of Port St. Lucie, Fla. Mateen acknowledged his allegiance to the Islamic State during a 911 call to local law enforcement from the nightclub in which he claimed responsibility for the shootings, one of the officials said. The FBI interviewed Mateen twice in 2013 after he made inflammatory comments to co-workers about possible terrorist ties, but the interviews were inconclusive, Assistant Special Agent Ronald Hopper said at a news conference Sunday. 
• Weapons: Police said the gunman was armed with an assault rifle, a handgun and some sort of unidentified device. 
• Terrorism suspected: Investigators were reviewing a range of possible terror links to the gunman.
• Shooting suspect's father: The gunman’s father recalled that his son recently got angry when he saw two men kissing in Miami and said that might be related to the assault.
• The nightclub: Pulse refers to itself as "not just another gay club." One of the owners started it to promote awareness of the area's lesbian, gay, bisexual and transgender community. Her brother died from AIDS. The attack is another example of violence against the LGBT community.
• Other threats: Authorities said they had no indication of any other threat in Florida or elsewhere in the nation. However, the city of Orlando and Florida state officials declared states of emergency.
• What the president said: President Obama on Sunday called the mass shooting "an act of terror" and "an act of hate."
• What the presidential candidates said: Presumptive Democratic nominee Hillary Clinton tweeted that she "woke up to hear the devastating news from Florida. As we wait for more information, my thoughts are with those affected by this horrific act." Presumptive Republican nominee Donald Trump tweeted: "Horrific incident in Florida. Praying for all the victims and their families. When will this stop? When will we get tough, smart and vigilant?"
• Hotlines for family members, tips: Police said they are focusing on identifying the victims. Family members who are trying to locate relatives can call 407-246-4357. A family assistance center has been set up at the Hampton Inn at 43 Columbia Street in Orlando. The FBI has asked anyone who was at the club before the shooting and anyone with tips to call 1-800-CALL-FBI ( 1-800-225-5324).