The killer gunman who opened fire inside the Manhattan building that houses the NFL was once a promising high-school football player, it has been revealed.

Authorities have identified Shane Tamura, a 27-year-old licensed private investigator from Las Vegas who once dreamed of a life in football, as the shooter who carried out a ᴅᴇᴀᴅly rampage in the heart of New York City on Monday night.

Tamura walked into the lobby at 345 Park Avenue in Midtown Manhattan with sprayed a long-form M4 rifle, shooting an NYPD officer in the back before heading to the 33rd floor and the offices of Rudin Management who run the building and continuing the gunfire, killing a total of four people. He then reportedly took his own life.

The building at 345 Park Avenue is also home to the NFL, which has its headquarters in the building.

Sources confirmed Tamura did not enter the NFL floor, yet investigators are looking into into whether he was targeting it given his past as a standout football player for Granada Hills Charter and Golden Valley in California.

Tamura grew up in Hawaii, where he attended high school and was immersed in a life dominated by sports. In a video posted online from the 2015 season, he can be heard giving a post-game interview in which he spoke of his victory with the Granada Hills Charter football team in Southern California.

It is unclear whether his football career continued after he graduated from Granada Hills Charter in 2016. DailyMail.com has approached the school’s athletics department for comment.

The killer gunman who opened fire inside the Manhattan building that houses the NFL was once a promising high-school football player,