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.

Investigators are examining why the gunman who killed four people before taking his own life at a New York City office tower targeted the National Football League and whether he suffered from a brain disease.