Manhattan shooter identified as Shane Tamura, 27, of Las Vegas: What we know about the gunman

The gunman who killed four people and himself inside a New York City office tower on Monday afternoon has been identified as Shane Devon Tamura, a 27-year-old licensed private investigator from Las Vegas who once dreamed of a life in football.

Authorities say Tamura, who had a 'documented mental health history', arrived in Midtown Manhattan by car on Monday afternoon following a mammoth cross-country trip. 

New York mayor Eric Adams indicated that authorities believe his target was the NFL, which has its headquarters in the tower. A note found on the gunman's body mentioned the league.

The three-page note outlined Tamura's perceived grievances with the NFL over its handling of the brain disease chronic traumatic encephalopathy (CTE), which is strongly linked to sports in which players experience repeated head impacts.