NYC shooting victims Didarul Islam, Wesley LePatner, Aland Etienne, and Julia Hyman were killed by a gunman inside Manhattan's 345 Park Ave.

A police officer and a Blackstone employee were among those killed Monday during a shooting at a New York City high-rise. An NFL employee was seriously hurt.

The killing of four people including a police officer in a Midtown Manhattan office building rattled a city where mass attacks are rare and violent crime has declined.

The attack on a seemingly secure building has rattled workers and prompted managers to examine whether they are adequately protected.

Officials say a man with a rifle killed an off-duty New York City police officer and three other people before taking his own life at a Manhattan office tower

The man who killed four people in the New York City skyscraper that is home to NFL headquarters carried a note blaming the league for his mental health problems

The gunman who opened fire in midtown Manhattan on Monday, killing four people before turning the gun on himself, left a note mentioning “CTE” several times, officials familiar with the investigation told NBC News.