Shane Tamura, the 27-year-old man who shot and killed four people inside a Midtown office building, didn’t show up for his shift as a Las Vegas casino security guard on Sunday, according to authorities.

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

Shane Tamura, 27, is the suspect alleged to have shot and killed four victims while wounding an NFL employee. Tamura then fatally wounded himself. Further investigation into the shooting revealed that Tamura was targeting the NFL's offices, but "appeared to have gone to the wrong floor" in the 44-story skyscraper.