A New York City office building where a gunman killed four people then himself has reopened a week after the deadly shootings. On Monday, workers trickled back into 345 Park Avenue in Midtown Manhattan, a skyscraper home to high-profile tenants including the NFL and asset management firm Blackstone.

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.