Four people were killed, including an off-duty New York City police officer, when a gunman opened fire in an office tower before fatally shooting himself, officials said.

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.

Tamura worked as a surveillance department employee at the Horseshoe hotel and casino in Las Vegas, a spokesperson for the Horseshoe said on Tuesday. Several squad cars from the Las Vegas Metro Police were seen at the entrances to a gated neighborhood where Tamura was believed to have lived.