A shooting Monday at an office building in New York City that is home to the Blackstone investment firm and the NFL left four people dead, including an NYPD officer.

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.

A man stalked through a Manhattan office tower firing a rifle, killing four people, including a New York City police officer, and wounding a fifth before taking his own life, officials said.