FORT LEE, N.J. (CBSNewYork) — Residents of a Fort Lee block were shocked Friday night, after police said one of their neighbors shot and killed a security officer at the federal building in the Hudson Square area before turning the gun on himself.

As CBS2’s Dave Carlin reported, a block of Harvard Place was taped off by police following the shooting, as officers with the Fort Lee police SWAT team moved in to secure the home of Kevin Downing, 68, and start gathering evidence.

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Downing walked into the federal office building at 201 Varick St. and approached the metal detector at the security screening area, NYPD Chief of Department James O’Neill said. The suspect then pulled out a gun and shot the security guard in the head, officials said.

The security guard, Idrissa Camara, 53, was later pronounced dead at Lenox Hill HealthPlex.

Downing then walked through the metal detectors toward the elevator and approached another employee, O’Neill said. The suspect then shot himself in the head, O’Neill said.

“That’s a shock,” said neighbor John Damato.

“He was a quiet, nice gentleman,” said neighbor Edward Moon.

Neighbors struggled to understand the violent final actions of a man they knew as a polite real estate agent, who they said lived alone since the death of his wife.

“His wife passed away three years ago,” Moon said.

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Real estate listings showed Downing bought the home in 1987, putting it on the market without success on several different occasions over the years — most recently in 2013.

Late Friday, the home was swarming with detectives and neighbors wanting answers.

“God only knows what happened in his life, or what has happened in his life, that pushed him to that point,” Damato said.

Investigators confirmed some troubling facts about Drowning that neighbors said they never knew.

Police said it appears he was a retired U.S. Army Reserves captain, and also worked as an economist for the Department of Labor.

The Bureau of Labor Statistics where Downing worked has an office on the eighth floor the Varick Street building, but it is not clear whether Downing had once worked in the building.

Lawsuits and other documents indicate Downing may have been outraged at being fired by the Department of Labor, and considered the firing retaliation for blowing the whistle on alleged corruption and public waste.

A petition on on behalf of a Kevin Downing spells out the allegations, indicating Downing may have believed the Department of Labor was in some way blocking him from getting other jobs.

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Police were working closely with the FBI, the Department of Homeland Security and other authorities to determine the suspect’s motive, NYPD Chief of Department James O’Neill said.