Omar Mateen: From high-school football player to perpetrator of America's worst massacre

The photo from Omar Mateen's high-school yearbook is hardly remarkable - a toothy, dimpled smile with a peach fuzz mustache below a mop of black hair.

But his transformation from high-school football player to perpetrator of America's worst mass shooting raises questions over whether authorities, and the security company where he worked, missed red flags over the depth of his apparent sympathies with Muslim extremists and whether the United States has a clear strategy to turn Americans away from radicalism.

Much is unknown about what drove Mateen, 29, to walk into a packed gay nightclub in Orlando, Florida, with a handgun and AR-15 semi-automatic rifle and open fire, killing 50 people before police stormed the club and fatally shot him. Fifty-three others were wounded, many critically.

The gunman's ex-wife said he was emotionally and mentally disturbed with a violent temper, yet aspired to be a police officer.

Sitora Yusufiy, the former spouse of Omar Mateen, 29, identified as the shooter slain by police at the end of Sunday's massacre, also told reporters in a news conference aired on CNN that she was "rescued" by family members from her ex-husband after four months of a stormy marriage that ended in divorce.

Mateen, 29, to walk into a packed gay nightclub in Orlando, Florida, with a handgun and AR-15 semi-automatic rifle and open fire, killing 50 people before police stormed the club and fatally shot him. Fifty-three others were wounded, many critically.

Women embrace before a make-shift memorial in front of the Stonewall Inn where a vigil was held following the massacre that occurred at a gay Orlando nightclub on June 12, 2016 in New York City. (AFP)

In Fort Pierce on Florida's southeast coast, 120 miles (195 km) from the shooting, the imam at the mosque that Mateen attended for nearly 10 years described him as a soft-spoken, regular worshipper who rarely interacted with the congregation.

"He hardly had any friends," Syed Shafeeq Rahman, who heads the Islamic Center of Fort Pierce, told Reuters. "He would come with his little son at night to pray and after he would leave."

Rahman said Mateen never approached him regarding any concerns about homosexuals.

Mateen was born in New York of Afghan descent but spent most of his life in Florida, attending Martin County High School in in Stuart, a small city about a 20-minute drive from the Fort Pierce condominium where had most recently lived.

A classmate described him as a typical teenager who played football. An image of Mateen in his school yearbook was seen by Reuters.

Samuel King, who was one year ahead of Mateen, said the two often spoke after Mateen graduated in 2004. King worked as a waiter at Ruby Tuesday's restaurant at Treasure Coast Square, a mall where Mateen worked at GNC, the nutrition store, he said.

King, who is openly gay, said the Mateen he knew until 2009 did not appear to be anti-gay.

"What is shocking to me is that the majority of the staff at Ruby Tuesday's when I worked there were gay. He clearly was not anti-(gay) at least not back then. He did not show any hatred to any of us. He treated us all like the individuals we were. He always smiled and said hello."

While at GNC, Mateen lifted weights and "got really buff," King said, describing Mateen as gregarious and talkative in the immediate years after high school. "Something must have changed" since he last saw him, he added.

Mateen's father, Mir Seddique, told NBC News the massacre was not related to religion.

He said his son turned angry when he saw two men kissing in Miami a couple of months ago. Mateen's ex-wife, who spoke to the Washington Post, said her former husband was violent and mentally ill and beat her repeatedly while they were married.