Shane Tamura, the Park Ave. gunman who killed an NYPD officer and three others before taking his own life, left behind a suicide note saying he suffered from CTE, a brain injury often linked to playing football, and was targeting the NFL — but took the wrong elevator, officials said Tuesday.

An NYPD officer, a security guard, and two women who worked in the building were killed. Here are the latest developments.

Study my brain please,” read a note left by the gunman accused of killing four people in a building that houses NFL’s headquarters