ORLANDO, Fla. -- A gunman opened fire inside a nightclub early Sunday morning, leaving 50 people dead, including the gunman, and 53 hospitalized in the worst terror attack in the U.S. since 9/11 and the worst mass shooting in the history of the United States.
The city of Orlando was slowly releasing the names of the victims after the next of kin were identified.
-- Edward Sotomayor Jr., 34
-- Stanley Almodovar III, 23
-- Luis Omar Ocasio-Capo, 20
-- Juan Ramon Guerrero, 22
-- Eric Ivan Ortiz-Rivera, 36
-- Peter O. Gonzalez-Cruz, 22
-- Luis S. Vielma, 22
-- Kimberly Morris, 37
-- Eddie Jamoldroy Justice, 30
-- Darryl Roman Burt II, 29
-- Deonka Deidra Drayton, 32
-- Alejandro Barrios Martinez, 21
-- Anthony Luis Laureanodisla, 25
-- Jean Carlos Mendez Perez, 35
-- Franky Jimmy Dejesus Velazquez, 50
-- Amanda Alvear, 25
-- Martin Benitez Torres, 33
-- Luis Daniel Wilson-Leon, 37
-- Mercedez Marisol Flores, 26
-- Xavier Emmanuel Serrano Rosado, 35
-- Gilberto Ramon Silva Menendez, 25
-- Enrique L. Rios Jr., 25
-- Miguel Angel Honorato, 30
-- Javier Jorge-Reyes, 40
-- Joel Rayon Paniagua, 32
-- Jason Benjamin Josaphat, 19
-- Cory James Connell, 21
-- Juan P. Rivera Velazquez, 37
-- Luis Daniel Conde, 39
-- Shane Evan Tomlinson, 33
-- Juan Chevez-Martinez, 25
-- Jerald Arthur Wright, 31
-- Leroy Valentin Fernandez, 25
-- Tevin Eugene Crosby, 25
There were approximately 300 to 350 people inside the club at the time of the shooting. The attack occurred in two areas of the nightclub.
Dramatic details about how some employees and patrons of the Pulse nightclub survived have been told by a source close to the nightclub's owners and employees:
One person hid in the bathroom covered herself with dead bodies to protect herself. She survived.
Some entertainers hid in the dressing room when the shooting started. They were able to escape the building when police removed the air conditioning unit and crawled out.
One of the bartenders said that she was hiding under the glass bar. Police came in and said, "If you are alive, raise your hand." Then police got them out.
The shooter was identified as Omar Mir Seddique Mateen, 29, of Fort Pierce, Fla. He is a U.S. citizen, born Nov. 16, 1986 in New York. His parents are originally from Afghanistan.
He was shot dead by Orlando police in an operation to free hostages the shooter had taken.
The family of the shooter told investigators Mateen wasn't particularly religious from what they observed. They expressed surprise about any connection to ISIS, according to two law enforcement officials.
Mateen did express outrage to his father after seeing two men kissing in Miami, investigators say. Mateen's ex-wife told investigators he had issues with anger.
Mateen was married to Noor Salman according to neighbors of Noor's mother. Additionally Noor was listed on a mortgage document as Mateen's wife. A source who knows the family well spoke to Noor's mother on the phone. The mother was weeping and said "Why is God doing this to me?"
His father, Seddique Mateen spoke to WOFL and said he saw his son Saturday and he's "surprised" and "sad" for what happened.
2 a.m.: Closing time at Pulse, about two minutes after 2 a.m., the first shots rang out. Witnesses think they are part of the music. Some survivors are able to escape, security and two other officers all fire on the shooter who takes hostages
2:09 a.m.: Pulse management posts on Facebook: "Everyone get out of Pulse and keep running."
2:22 a.m.: Mateen calls 911 pledging allegiance to ISIS and mentioning the Boston Marathon bombers.
5 a.m.: A SWAT team uses an armored vehicle to smash down a door, 30 more people escape
Officers shoot and kill Mateen in the doorway
Authorities are looking into possible self-radicalization, into the shooter's electronic devices for any suspicious activity and trying to put together a timeline of his movement.
The Orlando nightclub shooter called 911 20 minutes into the attack to pledge allegiance to ISIS and mentioned the Boston bombers, according to a U.S. official. Massachussetts State Police say they are sharing information and intelligence with federal authorities.
Mateen was interviewed by the FBI in 2013 and 2014, FBI Assistant Special Agent in Charge Ronald Hopper told reporters Sunday.
"Those interviews turned out to be inconclusive, so there was nothing to keep the investigation going," Hopper said.
He was not under investigation at the time of Sunday's shooting and was not under surveillance, Hopper said.
He was the subject of the 2013 investigation after making comments to co-workers about terrorist ties. The next year he was interviewed over possible connections to an American suicide bomber. He was not considered a priority subject.
Law enforcement officials say Mateen was known to the FBI, one of hundreds of people suspected of being ISIS sympathizers who are on the FBI's radar, according to two law enforcement officials.
There was no indication he was plotting to carry out an attack the officials said. The investigators haven't found evidence yet to show that he did this on behalf of ISIS. But the earlier knowledge about his possible sympathies explains why they are treating this as likely Islamic-related terror.
There has been no claim of responsibility for the attack on jihadi forums, but ISIS sympathizers reacted by praising the attack on pro-Islamic State forums, according to terrorism analyst Paul Cruickshank.
The Imam at the Fort Pierce Islamic Center, Syed Shafeeq Rahman, said Mateen was playful and more social when young, but recently kept to himself. He would come two or three times a week for two hours and talk to no one.
He was at Friday prayers and said it was his usual routine. He was quiet and kept to himself. Rahman said Mateen had been coming to the mosque since 2003. He appealed for peace saying: "We have to stop the killing and bloodshed."
Two former high school classmates at two different schools remember Mateen saying something to the effect Osama bin Laden was his uncle, which caused a lot of brushback from other students.
The classmates said that the Sept. 11 attacks seemed to be a significant moment for him and recounted how his mental health may have been affected by them -- that it changed.
Mateen purchased a handgun and a long gun within the last few days, ATF Assistant Special Agent in Charge Trevor Velinor told reporters.
"He is not a prohibited person. They can legally walk into a gun dealership and acquire and purchase firearms. He did so. And he did so within the last week or so," Velinor said.
Investigators recovered an additional gun in Mateen's car. It's a .38 caliber Smith and Wesson revolver, according to a law enforcement official. ATF is working to trace it.
The other two firearms were a Sig Sauer rifle and a Glock pistol, which were traced to the shooter. He bought those two in the past couple weeks (June 4 and 5).
A law enforcement source said Mateen rented a vehicle and drove to Orlando to carry out the attack. That vehicle was right outside Pulse, according to Orlando's police chief.
Mateen worked as a security guard -- that allowed him to have a firearms license, and minimal background checks when he bought firearms. According to a neighbor who saw him regularly, Mateen worked as a security guard at the Port St. Lucie courthouse. The neighbor said Mateen often worked security in the front of the building, manning the metal detectors.
Eleven Orlando police officers and three sheriff's deputies who exchanged gunfire with the shooter in the shooting will be temporarily relieved of duty pending an investigation, officials said.
A message was posted in Arabic on a Dark Web Telegraph site that is associated with the ISIS news agency Amaq. The message is being cited by some officials as a claim of responsibility by ISIS.
The translation reads: "Sources for Amaq News Agency: the armed attack that targeted a gay nightclub in the city of Orlando in the American state of Florida and that bore more than 100 killed and wounded was carried out by an Islamic state fighter."
But Salma Abdulaziz, who translated the message and closely monitors ISIS messaging, adds this important skeptical context: The language is inconsistent with previous ISIS announcements.
In particular, the Arabic word for gay was used rather than an epithet, the usual approach for ISIS. There was no claim that the attack was directed, just an after-the-fact claim the gunman was an ISIS fighter.
Barbara Poma, owner of Orlando Pulse nightclub, released the following statement: "Like everyone in the country, I am devastated about the horrific events that have taken place today.
"Pulse, and the men and women who work there, have been my family for nearly 15 years. From the beginning, Pulse has served as a place of love and acceptance for the LGBTQ community. I want to express my profound sadness and condolences to all who have lost loved ones. Please know that my grief and heart are with you."
Pulse on its website calls itself "the hottest gay bar in Orlando."
Pulse described as a "welcoming" place: Performers who worked at Pulse, but weren't there on Saturday night described the place as "open" and "welcoming," echoing what many have said about the club.
The incident at the Los Angeles Pride Festival -- involving the arrest of a man with an arsenal of weapons and explosive weapons -- is believed to be unrelated to the attack in Orlando, local and federal authorities say.
President Barack Obama: Called the Orlando attack an "act of terror and an act of hate." He ordered flags to be flown at half-staff. This is the 15th time Obama has made an address in response to a mass shooting.
Obama's first campaign appearance with presumptive Democratic presidential candidate Hillary Clinton has been postponed because of the Orlando shootings, the campaign announced.
Florida Gov. Rick Scott: "This is clearly an act of terrorism. It's sickening," he said. "It should make every American angry."
Pope Francis: "We all hope that ways may be found, as soon as possible, to effectively identify and contrast the causes of such terrible and absurd violence."