STUART, FLA. — Mass shooter Omar Mateen was a target of law enforcement long before Sunday’s attack, his first arrest coming when he beat up a high school classmate in Florida years earlier, newly released records show.

In his application for a Florida state corrections job in 2006, Mateen acknowledged he’d been arrested on charges of battery and disrupting a school function after he beat up the student in his math class in 2001, according to the records obtained by Newsday from the state Department of Corrections.

It’s unclear how Mateen pleaded to the crimes — both misdemeanors — because juvenile records are not publicly available in Florida.

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“I did not get handcuffed and I did not go to jail,” Mateen wrote in the application for a correction officer position at Martin Correctional Institute. “It was an experience of me growing up and I learned a big lesson from it.”

The state records offer a glimpse of Mateen’s teenage years before he carried out the deadliest mass shooting in modern American history, killing 49 people and wounding 53 at Pulse nightclub, a LGBT party spot in Orlando.

FBI agents on Friday questioned at least one member of the mosque where Mateen worshipped, a federal law enforcement source said.

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The bureau’s interest in the Islamic Center of Fort Pierce, where Mateen attended prayer services several days a week, stems in part from Mateen’s relationship with Moner Mohammad Abusalha, the first U.S.-born terrorist to carry out a suicide bomb attack in Syria, the source said.

Abusalha also worshipped at the Islamic Center, and the men knew each other before Abusalha died in Syria. Their relationship was once the subject of an FBI investigation, and agents are scrutinizing the men’s connections more closely in light of Sunday’s deadly attack at Pulse, the source said.

Right now, the FBI is not looking at the center itself as a genesis of Mateen’s radicalization, the source said, but agents do want to better understand Mateen’s relationship with other center members, and with the larger Islamic community in the area. That’s what led them to conduct the interview(s) Friday, the source said.

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Records show the New Hyde Park-born Mateen worked as a private security guard patrolling golf clubs, apartment complexes and other properties across Florida’s Treasure Coast. He was employed by G4S, the global security firm formerly known as Wackenhut, and aspired to a more prestigious career in law enforcement, records show.

His application to the state corrections department includes letters of recommendation from people who lauded Mateen’s character and helpfulness, records show.

“I would sleep soundly at night knowing that a person like Omar is protecting us (from) the element which resides behind your concrete and steel walls,” wrote Port St. Lucie Police Officer Steve Brown, whose letter said he’d met Mateen at a Gold’s Gym.

It was while earning a degree in criminal justice technology from Indian River State College that Mateen was offered a paid training program slot with the corrections department, which he accepted, records show.

He was dismissed roughly six months later for an unspecified administrative issue that was not misconduct, the records show.

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In administrative records filed with the state, Mateen said he’d engaged in previous criminal activity that went undetected, and that he’d used marijuana.

A few months after his dismissal from the corrections department program, Mateen found employment with G4S.

The job helped him get a firearms permit from the state that allowed him to carry a gun for work, records show. On his application for a firearm permit, Mateen’s listed his email address as “onpatrol1986.”

G4S has said it conducted at least two background checks on Mateen, both of which he passed. He also passed a psychological test administered when he was hired, the company has said.

The company also said it was aware the FBI investigated Mateen after he made inflammatory comments while working at the St. Lucie County Courthouse as part of his private security duties, but was not aware of possible links between Mateen and known terrorists.

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Those alleged associations were also part of an FBI probe — one that ended without charges being brought against Mateen, officials said.

Meanwhile, school records show Mateen was disruptive and sometimes violent in school, receiving suspensions totaling 48 days.

Records from Martin County show Mateen attended three schools there, including time at an alternative school, The Associated Press reported. The records show at least some of the suspensions were for fighting that involved injuries. Other suspensions were for unspecified rules violations.

Mateen attended high school and part of middle school in Martin County. He attended elementary and early middle school in neighboring St. Lucie County, where teachers regularly found him disruptive and struggling academically because of a lack of focus.

On Long Island, Rep. Peter King on Friday called for the FBI to monitor “psychotics” and others who suffer from severe mental illness and pose a threat to society, saying they are being recruited by terrorist groups.

The Seaford Republican said the Orlando mass shooting was proof that the severely mentally ill are a “clear and present danger” and should be subject to surveillance by the FBI. He called on the FBI to establish a category to do this.

Speaking to a business group in Melville, King said the FBI was forced to drop its monitoring of Mateen because he didn’t meet current guidelines for surveillance.

“He was seen as a crazy person, not a clear and present danger,” said King, a longtime advocate for tougher homeland security measures. “He didn’t meet the level that was required to be put on the [terror] watch list.”

In Florida, dozens of people continue to gather daily at a corner memorial near a small lake about two blocks from the massacre site in south Orlando.

In addition to flowers, flags and candles, there are now 49 crosses, one for each of the victims, with their name and a photo.

Four women sat before the cross for Eric Ivan Rivera Ortiz, telling stories about his bubbly personality, his sense of style and his perfectionism. And they were laughing, because that’s how Rivera Ortiz, a married gay man who worked two jobs at Orlando retail stores, would have wanted it.

María Rivera, his mother, said the family felt embraced by the community in Orlando and on the island of Puerto Rico, and that befits the “happy and compassionate person he was.”