The 27-year-old Nevada man opened fire at a New York City office building, killing at least four people and then himself.

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

The alleged gunman was identified as 27-year-old Shane Tamura, of Nevada. Police said the motive for the shooting remains under investigation and investigators are working to understand why the suspect targeted the commercial building.