UnitedHealthcare CEO Brian Thompson was killed by a gunman in New York City. He was 50 years old.

Brian Thompson, 50, was shot by a masked gunman around 6:45 a.m. near the New York Hilton Midtown, where he was set to speak at an investment conference, New York City Police Commissioner Jessica Tisch said at a news conference.

With the gunman’s identity unknown and the motive still a mystery, authorities are trying to piece together the killer’s movements that morning – and where he went next