MADISON, S.D. (AP) — From the moment 73-year-old Carl Ericsson rang his old high school classmate’s doorbell in January, verified the man’s identity and then shot him dead, the question had been what prompted him to confront a man he hadn’t even spoken to in years.

The startling answer, a prosecutor said Friday, was a 1950s locker room humiliation that festered in Ericsson’s mind for a half-century.