The gunman who killed at least four people and himself at a Midtown Manhattan office tower was targeting the National Football League, but ended up on Rudin Management’s floor by mistake, two senior law enforcement officers said.   

Instead of going to the NFL’s fifth-story office at 345 Park Ave., he picked the wrong elevator bank that took him to Rudin’s office on the 33rd floor, the officers said. That’s where the body of the shooter, believed to be Shane Tamura, a 27-year-old who last resided in Las Vegas, was found.   

A manifesto and notes found on him indicated a fixation with Chronic Traumatic Encephalopathy, or CTE, caused by head trauma, the officers said. His social media feed showed his football career ended after a head injury, and he wrote that the NFL didn’t do enough for CTE.   

The gunman has a documented history of mental-health troubles, drove across the country before entering New York City earlier Monday, Police Commissioner Jessica Tisch said.   

The tower also houses the headquarters of Blackstone Inc., where an employee was among those killed, according to a person briefed on the matter.   

Bloomberg's John Tucker has the details in this two-minute report.