Shane Devon Tamura, the man identified as the gunman who killed four people in a deadly shooting at a midtown Manhattan office building that houses the NFL 's headquarters, was once a standout high school football player.

A Nevada man recently traveled to New York City, entered a Manhattan building wearing body armor, carrying an M4 rifle, and fatally shot four people Monday evening, including a New York Police Department officer and injured another,

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