FORT PIERCE, Fla. — Before he pledged allegiance to the Islamic State and carried out the deadliest mass shooting in American history, Omar Mateen made a living protecting his neighbors.

The 29-year-old Fort Pierce-area resident worked as an officer for the Jupiter-based G4S security company for nine years beginning in 2007, guarding golf courses and retirement communities and, according to one colleague, making inflammatory statements about homosexuals, Jews and the American military.

“When I saw his picture on the news, I thought, of course, he did that,” said Eric Baumer, whose security guard shifts at the PGA Golf Club at PGA Village overlapped with Mateen’s in 2015. G4S confirmed Mateen’s employment with them in a statement issued Sunday. “He had bad things to say about everybody — blacks, Jews, gays, a lot of politicians, our soldiers. He had a lot of hate in him. He told me America destroyed Afghanistan.”

Mateen’s march toward radicalization was apparent in those talks outside the golf club, Baumer said, but the accused mass killer showed signs of violence years earlier, according to several other people who knew the suspected terrorist.

Oana Braescu, 32, of Fort Pierce, recalls hearing Mateen screaming at his then-wife when Braescu lived next to the couple’s Fort Pierce home in 2009.

“He’d scream and scream, and one time . . . I could hear her asking him to stop hitting her,” said Braescu, adding that she recalls seeing Mateen’s ex-wife come running out of the house in tears on several occasions. “There was something the matter there, in his head.”

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She said she also recalls seeing Mateen come home from work with a holstered gun on his hip, looking exhausted.

“I was thinking, this person is dangerous,” she said.

Sitora Yusufiy, Mateen’s ex-wife, spoke to CNN last evening from Boulder, Colorado, about her ex-husband.

Upon hearing the allegations against him, she said: “I was devastated, shocked. I started shaking and crying. More than anything I was so deeply heartbroken for the people that lost loved ones.”

Yusufiy described her former husband as normal at first, but a few months into their marriage he began abusing her “physically” and prevented her from talking to her family, she told CNN.

He worked at a juvenile jail, she said, and dreamed of becoming a police officer. “He wanted to be a cop,” she said, adding that he applied to a police academy.

Others recalled Mateen as a typical American 20-something — a “normal guy from New York” who “talked a lot about New York,” said Frank Severance, of Port St. Lucie.

“He liked sports, he liked girls,” said Severance, who recalls talking with Mateen outside a Fort Pierce condominium where the suspected terrorist most recently lived. On Sunday afternoon, members of federal, state and local law enforcement agencies were gathered in force around the community. “I didn’t think he was a bad guy. But I think other people had a bad feeling about him.”

Indeed, by 2014, law enforcement was receiving information about Mateen’s inflammatory statements to colleagues and his discussions about violent acts. That year, the FBI investigated Mateen for his potential connections to Moner Mohammad Abusalha, the first American-born terrorist to carry out a suicide bomb attack in Syria, according to a federal law enforcement official with knowledge of the investigation into Sunday’s mass shooting.

Abusalha had at one point lived in Fort Pierce, where Mateen also lived. Abusalha is believed to have received terrorist training in the Middle East before he came back to Florida and tried to recruit others to the cause, the source said. He was apparently unsuccessful in those efforts at the time, but may have influenced Mateen nonetheless, setting him further on the path toward radicalization, the source said .

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“We’re going over every piece of information we have from that time,” the source said, adding that the men had limited contact. “Was he an influence? That’s a question being asked.”

Also of renewed interest to investigators — given the location of Sunday’s shooting — is a social media post Abusalha made in 2011 calling for homosexuals to be killed, the source says.

He says the FBI has already interviewed dozens of people who’ve had contact with Mateen over the years — family, friends, colleagues, etc. — trying to learn more about his day-to-day life and path to radicalization. It is also analyzing computers and other electronics seized from Mateen’s home, as well as several properties owned by his relatives in Port St. Lucie and Fort Pierce, as part of their probe.

The FBI is also examining his medical history and interviewing relatives to determine the severity of Mateen’s possible mental illness, the source said.

Mateen’s family is from Afghanistan, the source said, and maintains contact with at least some relatives in the region.

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“He would talk about what America did to Afghanistan after 9/11, saying we [the Americans] were murderers,” Baumer, the ex-security worker, said of Mateen, who was born in New York.

“He did talk about killing people, gay people, people he thought were bad,” Baumer added. “I didn’t know he meant it. How could you know?”