New Delhi, Aug. 7 -- The mother of the man who killed four people at a Manhattan office tower home to the NFL before taking his own life told 911 dispatchers during a 2022 incident when he threatened to kill himself that he suffered from a sports-related concussion and other issues, new information released by Las Vegas police Tuesday revealed.

Shane Tamura, 27, had a documented history of mental health problems and carried a handwritten note in his wallet when he carried out the shooting that claimed he had chronic traumatic encephalopathy, known at CTE, investigators said. He accused the football league of hiding the dangers of brain injuries linked to contact sports.

His mother told the dispatchers on Sept. 12, 2022, that her son was...