New York City is mourning NYPD Officer Didarul Islam and three other people killed in Monday's shooting inside an office building at 345 Park Ave.

A gunman opened fire inside the Manhattan skyscraper that is the headquarters of private-equity firm Blackstone and the NFL, killing four people, including a police officer, before fatally shooting himself on Monday evening, authorities said. Another person was in critical condition, and others suffered less serious injuries.

The Rudin family, which owns the building and Rudin Management, said in a statement that one of their employees was a victim of the shootings but did not disclose the person’s name at the request of relatives. Police officials said a woman was found dead on the building’s 33rd floor in Rudin’s offices.