Didarul Islam, a 36-year-old New York Police Department officer, was among four people killed Monday evening in Midtown Manhattan when a gunman stormed the lobby of the sprawling 345 Park Avenue office tower and opened fire.

Islam, an immigrant from Bangladesh who New York officials have described as a hero, leaves behind two young sons and his wife – who is pregnant with their third child.

NYPD Commissioner Jessica S. Tisch said Islam had been off-duty, but in uniform and working security in the building when he was shot and killed by 27-year-old Shane Devon Tamura.

“He was doing the job that we asked him to do,” said Tisch at a news conference Monday night.

“He put himself in harm’s way, he made the ultimate sacrifice – shot in cold blood, wearing a uniform that stood for the promise that he made to this city. He died as he lived, a hero.”