Investigators believe Shane Tamura, of Las Vegas, was trying to get to the NFL offices after shooting several people Monday in the building’s lobby but accidentally entered the wrong set of elevator banks,

A gunman who killed four people at a Manhattan office building before killing himself claimed in a note to have a brain disease linked to contact sports and was trying to target the National Football League’s headquarters but took the wrong elevator,

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