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 gunman who killed four people in a midtown Manhattan office building left a suicide note indicating that he was targeting the NFL, police said.

No motive has been announced. A suicide note was found expressing grievances with the NFL and saying Tamura suffered from CTE, a source said. Follow for live updates.

The Rudin family, which owns the building and Rudin Management, said in a statement that one of their employees was a victim of the shootings but did not disclose the person’s name at the request of relatives. Police officials said a woman was found dead on the building’s 33rd floor in Rudin’s offices.

As for security, badges and sign-in lists for visitors became standard fare in New York office buildings after the Sept. 11 attacks nearly a quarter-century ago. Many buildings installed turnstiles between guard desks and building elevators. In recent months, some buildings had stepped up their precautions even more because of the war in Gaza.