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.

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.

Fear and confusion were rampant after a gunman shot and killed four people and wounded another in a Midtown Manhattan office tower Monday evening before, authorities said, taking his own life.