Here's the latest about the Orlando terror attack:
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.
911 call: Omar Mateen, 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.
FBI investigation: The FBI interviewed the shooter 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, Mateen was interviewed over possible connections to an American suicide bomber. He was not considered a priority subject.
Suspected ISIS sympathizer: 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. Investigators haven't found evidence to show he was acting on behalf of ISIS. But the knowledge about his possible sympathies explains why they are treating the case as likely Islamic-related terror.
No claim of responsibility: There has been no claim of responsibility for the Orlando nightclub terror attack on jihadi forums, but ISIS sympathizers reacted by praising the attack on pro-Islamic State forums, according to CNN terrorism analyst Paul Cruickshank.
Local mosque reaction: In an interview with CNN's Drew Griffin, the imam at the Fort Pierce Islamic Center, Syed Shafeeq Rahman, said Mateen was playful and more social when young but had recently kept to himself. He would come to the mosque two or three times a week for two hours and talk to no one. Rahman said he was at Friday prayers -- his usual routine. Rahman said Mateen had been coming to the mosque since 2003. The imam appealed for peace saying: "We have to stop the killing and bloodshed."
High school classmates remember odd statement: Two former high school classmates 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 September 11 attacks seemed to be a significant moment for him and recounted how his mental health may have been affected.
Ex-wife speaks: Two FBI agents spent 1½ hours in the home of Sitora Yusufiy's fiancé in Boulder, Colorado. Yusufiy is the ex-wife of Mateen. Addressing reporters, Yusufiy said Mateen was a normal husband at the beginning of their marriage in 2009 but a few months later he started abusing her. Mateen was bipolar, she said, but he was not formally diagnosed. She said he wouldn't allow her to see her family. She also said Mateen had a history with steroids. She said he was religious but doesn't think his religion played in to the attack.
A copy of a marriage record filed in St. Lucie County, Florida, Circuit Court for Omar Mir Seddique Mateen from 2009 shows Yusufiy is originally from Uzbekistan. According to court records, Mateen filed a petition for dissolution of marriage in June 2011. A judgment was entered in July 2011.
Brother-in-law speaks: In a phone interview with CNN's Griffin, Omar Mateen's brother-in-law said, "I didn't see anything related to mental issues." The brother-in-law, who asked that his name not be used, said he heard Mateen's ex-wife on television and said she is either exaggerating or not telling the truth. He added, "We are in shock. I can't believe it. I saw him twice a week." He repeated the story that Mateen's father told of his son being angered when he saw men kissing in Miami.
Other people involved?: "There is an ongoing criminal investigation," U.S. Attorney Lee Bentley said at a Monday news conference. "It is still in the early stages. We don't know if anyone else will be charged in connection with this crime." He went on to say. "There is an investigation of other persons. We're working as diligently as we can on that. We have teams of prosecutors, as well as teams of agents, working around the clock getting search warrants, court orders. If anyone else was involved in this crime, they will be prosecuted."
The guns: The shooter purchased a handgun and a long gun within the last few days, Trevor Velinor Bureau of Alcohol, Tobacco, Firearms and Explosives 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.
Body armor: The shooter attempted to buy military-grade body armor from a local store in recent weeks, according to a U.S. official briefed on the investigation. The attempt suggests to investigators Mateen may have been plotting this attack for some time, according to the official. A person who identified himself as a manager at the store where Mateen purportedly sought to buy Level III body armor -- which offers higher protection than what most police issue to officers -- said there was no sale because the store does not sell body armor of any kind.
Additional gun found and other details: Investigators have recovered an additional gun in the shooter's car. It's a .38-caliber Smith and Wesson revolver, according to a law enforcement official. The 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 recently (June 4 and 5).
Employment: Mateen worked as a security guard -- allowing him to have a firearms license and minimal background checks when buying firearms. According to a neighbor who saw him regularly, Mateen was a security guard at the St. Lucie County Courthouse. The neighbor said Mateen often worked security in the front of the building, manning the metal detectors.
Caution around claim of responsibility: A message was posted in Arabic on a Dark Web Telegraph site associated with the ISIS news agency Amaq. Some officials have cited the message as a claim of responsibility by ISIS.
Here is CNN's translation: "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 CNN's Salma Abdulaziz, who translated the message and closely monitors ISIS messaging, said:
--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 he attack was directed, just an after-the-fact claim the gunman was an ISIS fighter.
Death toll: 49 victims and the shooter
-- 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
-- Simon Adrian Carrillo Fernandez, 31
-- Jonathan Antonio Camuy Vega, 24
-- Jean C. Nives Rodriguez, 27
-- Rodolfo Ayala-Ayala, 33
-- Brenda Lee Marquez McCool, 49
-- Yilmary Rodriguez Sulivan, 24
-- Christopher Andrew Leinonen, 32
-- Angel L. Candelario-Padro, 28
-- Frank Hernandez, 27
-- Paul Terrell Henry, 41
-- Antonio Davon Brown, 29
Grave condition: Five shooting patients are hospitalized in grave condition, according to the latest Orlando Health statement, and an unspecified number of patients are critically ill and in shock.
Victim identification: Authorities have identified 48 out of 49 victims, according to Orlando's mayor.
Victim updates are available on city of Orlando's website.
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:
-- There were about 300 to 350 people inside the club at the time of the shooting early Sunday. The attack occurred in two areas of the nightclub.
-- One survivor hid in the bathroom and covered herself with bodies for protection.
-- Some entertainers hid in the dressing room when the shooting started. They were able to escape from the building by crawling out when police removed the air conditioning unit.
-- A bartender said she hid under the bar. Police came in and said, "If you are alive, raise your hand." Then police got her and others out.
2 a.m. -- At closing time, about two minutes after 2 a.m., the first shots rang out at Pulse. Witnesses said they thought the noise was part of the music.
Some clubgoers were able to escape; security and two other officers all fired on the shooter, who then took hostages.
2:09 a.m. -- Pulse management posted on Facebook: "Everyone get out of Pulse and keep running."
2:22 a.m. -- Mateen called 911 pledging allegiance to ISIS and mentioning the Boston Marathon bombers.
5 a.m. -- A SWAT team used an armored vehicle to smash down a door at the club; 30 more people escaped.
Officers shot and killed Mateen.
He was Identified as Omar Mir Seddique Mateen, 29, of Fort Pierce, Florida.
A U.S. citizen, he was born November 16, 1986, in New York. His parents are originally from Afghanistan.
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 expressed outrage to his father after seeing two men kissing in Miami, investigators said. Mateen's ex-wife told investigators he had issues with anger.
At the time of his death, 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. CNN's Sara Sidner talked to those neighbors. 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-TV in Orlando and said he saw his son Saturday and he's "surprised" and "sad" about what happened. The father later gave a press conference where he expressed his family's shock, anger and outrage about what his son had done and assured the public he would have reported any suspicions to police and the FBI. "What he did was an act of terrorism and he struck inside the house, which is against my principles," Seddique Mateen said. "I don't approve of anyone doing such a thing against their homeland. This is my home."
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's website say it's "the hottest gay bar in Orlando."
Pulse described as welcoming: Performers who worked at Pulse but weren't there Saturday night described the place as open and welcoming.
June is Pride Month.
An 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 said.
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. It's 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."