The shooter was identified as 27-year-old Shane Tamura.

According to reports, Tamura died due to self-inflicted injury.

The 44-year-old attacker barged into the 44-storey building, which also houses major corporate offices like Blackstone and the NFL.

Armed with a rifle, the attacker opened fire at around 6:30 p.m. during the evening rush, cops and law enforcement sources told The New York Post.

Tamura, who authorities said had a “mental health history,” unleashed his rampage after setting foot in the lobby, first gunning down officer Didarul Islam, NYPD Commissioner Jessica Tisch said at a Monday evening press conference as quoted by the newspaper.

'Mental Health History'

According to officials in Las Vegas, the shooting suspect has a "documented mental health history", Tisch was quoted as saying by BBC.

"His motives are still under investigation, and we are working to understand why he targeted this particular location," she said.

According to reports, Shane Tamura travelled 'cross country' to reach New York.

Meanwhile,  New York Police Department has issued the photo of the police officer who was killed in the attack.

He was identified as Didarul Islam, a Bangladeshi immigrant who has served the New York Police.

Tisch wrote on X: "May Police Officer Didarul Islam’s memory be a blessing."

He was a father of two, and his wife is pregnant with their third child, New York officials told BBC.

Mourning the death of the officer, New York Mayor Eric Adams posted on X: "Tonight, our city is reeling and four innocent families are mourning, including the family of NYPD Officer Didarul Islam who was killed at 345 Park Avenue."

He further said: "He represented the best of New York City, an immigrant from Bangladesh who put on a uniform to protect and serve us all."

Adams said the incident is currently under investigation.

He said: "We’re carefully searching the office building, however, we believe the incident is over, and the shooter was acting alone. He is now dead, and New Yorkers have nothing further to fear."

Governor Kathy Hochul wrote on X: "Tonight we mourn four New Yorkers, including one of New York’s Finest, taken in a senseless act of violence. Our hearts are with their loved ones and everyone affected by this tragedy, and we honor the first responders who bravely ran toward danger."