The guard had been fatally shot as he crouched behind a desk to take cover as the gunman sprayed the building’s lobby with bullets, police said.

The gunman, who said in a note he believed he had CTE, targeted skyscraper that houses the NFL's headquarters.

NYC gunman Shane Tamura is seen on video talking about his high school football career in California after a game in September 2015.

Adams told reporters that investigators believe Shane Tamura of Las Vegas entered the building with the intent to reach the NFL 's offices but accessed the wrong set of elevator banks. "He seemed to have blamed the NFL ," Adams said. "The NFL headquarters was located in the building, and he mistakenly went up the wrong elevator bank."