The gunman who killed multiple people at the NFL's headquarters in New York earlier this summer has been diagnosed with CTE.

The New York City Office of Chief Medical Examiner said in a statement on Friday that after testing Shane Tamura's brain tissue, they discovered "unambiguous diagnostic evidence" of the disease.

Tamura, of course, believed he was suffering from the ailment prior to his July 28 rampage ... and mayor Eric Adams said he was actually targeting the NFL over it.

Tamura, as you know, ended up killing four and wounding another after he got off on the wrong floor of the Park Avenue skyscraper. He died by suicide a short time after opening fire.

Tamura, 27, never played professional sports -- but he did log snaps as a running back and defensive back on multiple high school football teams.