New York City police detectives searched a studio apartment in Las Vegas that belonged to the suspected gunman in Monday's mass shooting at a Midtown Manhattan.

The NYPD sent detectives to Las Vegas to work with federal law enforcement in the investigation into Monday's deadly shooting inside a Midtown Manhattan office building.

Players and coaches around the NFL learned Tuesday that the target was the NFL itself, Mayor Eric Adams said, with the shooter picking the wrong elevator bank and getting off on a different floor.

Five people—including the suspected perpetrator Devon Tamura and NYPD officer Didarul Islam—were left dead at an office building in Midtow.

FBI Deputy Director Dan Bongino said agents from the bureau’s New York field office were responding to the area to provide support.

An NFL employee was seriously injured in the mass shooting that took place in the New York City building where the league has its headquarters, and the shooter reportedly had grievances with the NFL over its handling of CTE.

The man who opened fire in a Midtown Manhattan office building, killing four people and wounding a fifth, appeared to be targeting the NFL headquarters and had a note claiming he suffered from CTE, police sources told ABC News.