The 27-year-old man who shot and killed four people at a Midtown office building on Monday carried a note in his pocket, police sources told ABC News.

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.

The gunman suspected of targeting the National Football League headquarters In New York, killing four, was a former standout football player at two Southern California high schools.

Four people, including an NYPD officer, were killed and another person was injured in a shooting at a Manhattan office building. The suspect's motive is under invest

The ordeal in the Blackstone Building in Midtown Manhattan in New York City has led to a complete lockdown - as authorities have warned people to remain vigilant

A mass shooting at 345 Park Avenue in Midtown Manhattan, home to the NFL headquarters and other major firms, left five dead, including a police officer. The alleged gunman, Shane Devon Tamura, 27, of Las Vegas,