Many workers were returning to the office a week after a gunman stormed the building that houses Blackstone’s headquarters and shot and killed four people, including Wesley LePatner, one of the firm’s top real-estate executives.

The New York City office building where a gunman fatally shot four people and himself reopened Monday, one week after the deadly rampage.Workers returned to 345 Park Ave., in Midtown Manhattan under the watchful eyes of NYPD officers and a surplus of additional security following the mass shooting.