Source: Gunman's suicide note mentioned grievances with NFL

A lone gunman killed four people in Midtown Manhattan on Monday before fatally shooting himself in the deadliest gun attack in New York City in 25 years. The shooting happened at a Park Avenue skyscraper that includes corporate offices for the National Football League.

CNN correspondent Omar Jimenez reports from the scene, CNN chief law enforcement and intelligence analyst John Miller looks at the police's investigation, and Erica Hill speaks with former FBI assistant director Chris Swecker. #CNN #News