NYPD: Suspect in NYC shooting has 'documented mental health history'

A gunman who killed a NYPD officer and three others in a Manhattan high-rise building last night left behind a note that referenced the NFL and CTE, according to sources. MSNBC Investigative Correspondent Marc Santia reports from outside the building. Former NYPD Detective Tom Verni and independent political strategist Reed Galen join Chris Jansing to discuss the latest updates. For more context and news coverage of the most important stories of our day click here: https://www.msnbc.com/ » Subscribe to MSNB ...