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.

Here's how NFL players, coaches and executives reacted to a mass shooting at the league's office building in Manhattan:

Shane Tamura, who killed four people at a Manhattan office building, was trying to target the NFL headquarters but took the wrong elevator, New York City Mayor Eric Adams said.

Two teams NYPD detectives headed to Las Vegas Tuesday, to execute search warrants at Shane Tamura's home and at a gun store where he legally purchased a revolver on June 12 using a Nevada concealed carry permit,

The injured NFL employee in the New York City shooting has been identified as Craig Clementi, per reports. Here's the latest on his condition.

Police say a gunman who killed four people in a Manhattan skyscraper before taking his own life claimed to have a brain disease linked to contact sports and was trying to target the National Football League’s headquarters in the building.

Shane Tamura, the 27-year-old gunman who fatally shot 36-year-old New York City police officer Didarul Islam and several others in a New York City skyscraper on Monday, was reportedly found dead with a note claiming that football had given him chronic traumatic encephalopathy, or CTE.

The New York police officer killed in a mass shooting in a Manhattan skyscraper on Monday was an immigrant who left behind a pregnant wife, two young sons and distraught parents, while friends and officials in Bangladesh and the United States described him as a hero.