The New York City office building that was the site of a mass shooting Monday had significant security measures in place.

Businesses around the country are reevaluating security after a brazen shooting at a New York City office building raised questions about what it takes to keep workplaces safe. The attack on a seemingly secure building — in a gilded part of Manhattan where the rich live in sprawling apartments and tourists window-shop designer

A gunman who opened fire in a Midtown Manhattan skyscraper later died of a self-inflicted gunshot wound, police said. Officials say investigators recovered a note in which appeared to blame his own traumatic head injury on the National Football League,

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.