Police and investigators work near the area of the mass shooting at the Pulse nightclub on in Orlando, Florida on June 12, 2016.
A somber President Barack Obama  expressed grief and outrage at the "horrific massacre" of 50 late-night revelers at an Orlando gay club, branding it an act of terror and hate. / AFP / Mandel Ngan        (Photo credit should read MANDEL NGAN/AFP/Getty Images)
MANDEL NGAN/AFP/Getty Images
Police and investigators work near the area of the mass shooting at the Pulse nightclub on in Orlando, Florida on June 12, 2016. A somber President Barack Obama expressed grief and outrage at the "horrific massacre" of 50 late-night revelers at an Orlando gay club, branding it an act of terror and hate. / AFP / Mandel Ngan (Photo credit should read MANDEL NGAN/AFP/Getty Images)
Now playing
02:53
Reports: Orlando gunman visited nightclub several times
Orlando nightclub shooter Omar Mir Seddique Mateen poses with his wife, Noor Salman, in a family photo posted online.
Vimeo/Mateen family
Orlando nightclub shooter Omar Mir Seddique Mateen poses with his wife, Noor Salman, in a family photo posted online.
Now playing
02:44
Source: Orlando shooter texted wife during attack
orlando shooter moscque bruer orig _00012013.jpg
CNN
orlando shooter moscque bruer orig _00012013.jpg
Now playing
01:50
Inside Orlando shooter's mosque
orlando shooter omar mateen warning signs todd dnt tsr_00002116.jpg
Spectrum Junior/Senior High School
orlando shooter omar mateen warning signs todd dnt tsr_00002116.jpg
Now playing
03:41
Files: Mateen disciplined 31 times in elementary school
social media violence paul cruikshank orig_00002602.jpg
social media violence paul cruikshank orig_00002602.jpg
Now playing
01:28
The social voice of violence
The Big Fix
Now playing
01:50
New video of Orlando shooter emerges
Ex wife of Orlando gunman speaks out sot_00004712.jpg
Ex wife of Orlando gunman speaks out sot_00004712.jpg
Now playing
01:35
Ex-wife of gunman details violent marriage
orlando gunman radicalized online todd pkg_00005126.jpg
orlando gunman radicalized online todd pkg_00005126.jpg
Now playing
04:18
FBI: Orlando gunman radicalized online
omar mateen orlando shooters wife griffin dnt tsr_00021727.jpg
Vimeo/Mateen family
omar mateen orlando shooters wife griffin dnt tsr_00021727.jpg
Now playing
03:03
Did Orlando shooter's wife know about plot?
Univision reporter Juan Carlos Aguiar goes inside the apartment of Omar Mateen, who killed 49 people at Pulse nightclub in Orlando.
Univision
Univision reporter Juan Carlos Aguiar goes inside the apartment of Omar Mateen, who killed 49 people at Pulse nightclub in Orlando.
Now playing
00:58
Inside Omar Mateen's apartment
was orlando shooter omar matten gay todd dnt tsr_00020715.jpg
was orlando shooter omar matten gay todd dnt tsr_00020715.jpg
Now playing
01:54
Was the Orlando shooter gay?
Residents of Orlando light candles during the first official vigil in the wake of the deadly attack at Pulse Orlando.
Wil Sands/Fractures Collective for CNN
Residents of Orlando light candles during the first official vigil in the wake of the deadly attack at Pulse Orlando.
Now playing
01:22
Orlando shooter cased Disney and nightclub
performer says shooter frequented pulse cooper phoner_00020113.jpg
performer says shooter frequented pulse cooper phoner_00020113.jpg
Now playing
02:15
'Pulse' performer says shooter frequented the club
fbi comey orlando shooter omar mateen previous investigation sot legal view_00021125.jpg
CNN
fbi comey orlando shooter omar mateen previous investigation sot legal view_00021125.jpg
Now playing
02:42
FBI: Shooter had been investigated
orlando shooting father of shooter speaks fox35 bts_00000000.jpg
orlando shooting father of shooter speaks fox35 bts_00000000.jpg
Now playing
01:22
Shooter's father: Islam had nothing to do with this
Orlando shooting gunman ex wife presser bts_00002018.jpg
Orlando shooting gunman ex wife presser bts_00002018.jpg
Now playing
01:09
Ex-wife of Orlando shooter speaks out
An image taken from Omar Mateen's Myspace page.  Law enforcement sources identified Mateen as the shooter in the Orlando terror attack.
Omar Mateen/Myspace
An image taken from Omar Mateen's Myspace page. Law enforcement sources identified Mateen as the shooter in the Orlando terror attack.
Now playing
02:21
Gunman called 911, claimed allegiance to ISIS
The Orlando Police Department released this photo of Omar Mateen, the person identified as the shooter in the Orlando terror attack.
Orlando Police Department
The Orlando Police Department released this photo of Omar Mateen, the person identified as the shooter in the Orlando terror attack.
Now playing
01:23
Officials: FBI had investigated Orlando gunman

Story highlights

Former co-worker says killer was an angry, violent bigot

Ex-wife says suspect Omar Mateen abused her, held her hostage from family

CNN —  

As the world mourns the 49 victims of the Orlando nightclub massacre, investigators are working to piece together a picture of the man responsible for the deadliest mass shooting in U.S. history.

What could have driven Omar Mir Seddique Mateen, a New York-born security guard who was the son of Afghan immigrants, to such a horrific act of violence – the biggest terror attack on U.S. soil since 9/11?

Descriptions have quickly emerged of a troubled and angry individual.

His ex-wife, Sitora Yusufiy, described a brief but violent relationship to a mentally ill man whom she was only able to escape from through her family’s help. She said he was physically abusive and a steroid abuser.

And an ex-colleague who worked as a security guard alongside Mateen between 2014 and 2015 said his aggressive behavior eventually drove him to quit his job.

“He was an angry person, violent in nature, and a bigot to almost every class of person,” Dan Gilroy told CNN affiliate WPTV-TV in West Palm Beach. The former police officer asserts that he foresaw Mateen eventually committing an act of mass violence.

Mateen had even come to the attention of authorities, with the FBI interviewing him in two terror-related cases in recent years.

Officials say they're looking into the possibility Omar Mateen radicalized on his own.
Omar Mateen/Myspace
Officials say they're looking into the possibility Omar Mateen radicalized on his own.

But both of the investigations were closed, and Mateen – who would go on to call 911 and pledge allegiance to ISIS during his rampage – was not under investigation or surveillance at the time of the attack.

Despite the red flags Mateen raised in his interactions with others, the mass killer was able to purchase a handgun and assault rifle legally in the days before the massacre, Trevor Velino of the Bureau of Alcohol, Tobacco, Firearms and Explosives told reporters.

He had tried to buy body armor, but the store where he tried to make the purchase doesn’t sell that product, according to a store manager.

Cell phone tower data indicated he spent several hours Saturday at Disney Springs – the shopping and entertainment complex inside the Walt Disney World Resort – just prior to the attack, law enforcement officials said.

Mateen is believed to have been alone during that period, they said.

Four regular patrons at the Pulse nightclub, where the massacre took place, told the Orlando Sentinel they had seen Omar Mateen there before. In interviews with the newspaper, they said that he’d been there multiple times.

Prior visits to Pulse are a line of inquiry investigators are pursuing, sources involved in the investigation told CNN’s Jim Scuitto and Evan Perez.

FBI had investigated him twice

Mateen first came on the FBI’s radar in 2013 when he made “inflammatory comments to co-workers alleging possible terrorist ties,” Assistant Special Agent in Charge Ronald Hopper said. But investigators “were unable to verify the substance of his comments,” he said.

In 2014, the FBI interviewed Mateen again over possible connections with Moner Mohammad Abu-Salha, a Florida man who became the first known American suicide bomber in Syria. The men frequented the same mosque.

“We determined that contact was minimal and did not constitute a substantive relationship or threat at that time,” Hopper said.

FBI Director James Comey said that the agency is “highly confident” Mateen was radicalized, at least in part, by viewing extremism on the internet.

According to one official, analysis of Mateen’s electronic devices showed searches for jihadist propaganda, including videos of ISIS beheading.

“He consumed a hell of a lot of jihadist propaganda,” the source said.

“There are strong indications of radicalization by this killer and of potential inspiration by foreign terrorist organizations,” Comey said.

He said that investigators have found no indication the attack was directed from outside the United States or that Mateen was part of any kind of network.

A report Monday on the official online ISIS radio channel, Al-Bayan, described the attack as a “raid on a Crusader gathering” carried out by “one of the Caliphate’s soldiers in America.”

But there was no claim the attack was directed, just an after-the-fact assertion the gunman was an ISIS fighter.

Married with a child

Mateen lived in a condo in Fort Pierce, Florida, with his second wife, a woman named Noor Salman, according to documents CNN obtained. He also had a son, 3½, according to Mateen’s father.

He had worked for nine years as a security officer at G4S Secure Solutions, one of the world’s largest private security companies.

According to a neighbor, he was a security guard at the St. Lucie County Courthouse, often manning the metal detectors at the front of the building.

Ex-wife: He abused me

His first wife, Yusufiy, painted a damning portrait of the killer, describing a physically abusive marriage to a man with anger issues.

Yusufiy, who is originally from Uzbekistan, said the relationship had started well initially after they met online about seven years ago.