Follow along for live updates on the New York City shooting, where police investigate motive after five people, including the gunman, were killed in the Monday shooting.

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.

No motive has been announced. A suicide note was found expressing grievances with the NFL and saying Tamura suffered from CTE, a source said. Follow for live updates.