|Strangers on a Train (1951) [Bruno Anthony]: Fatally injured when a carnival merry-go-round goes out of control and crashes; he dies shortly afterwards, while Farley Granger tries to make Robert confess to killing Kasey Rogers.
Vengeance Valley (1951) [Lee Strobie]: Shot in the chest by Burt Lancaster when Robert draws his gun while standing in a shallow pond. We only see Robert's back during the shooting.
My Son John (1952) [John Jefferson]: Reportedly shot to death by communist agents while trying to flee in a taxi. (I haven't seen this movie myself.) (Thanks to Mac)