Sebije Nelovic always felt safe at 345 Park Avenue. For nearly three decades, the Albanian native cleaned the ritzy Manhattan skyscraper that housed several corporate headquarters in one of New York’s toniest neighborhoods.

There were 23 shell casings and 13 bullet fragments recovered from the lobby of 345 Park Avenue and 24 spent shell casings on the 33rd floor, police said.

The New York police officer killed in a mass shooting in a Manhattan skyscraper on Monday was an immigrant who left behind a pregnant wife, two young sons and distraught parents, while friends and officials in Bangladesh and the United States described him as a hero.