Source: Action Comics #309 (1964)
Of course, we should talk about the time of this issue. Though it's cover-dated January 1964, it actually came out barely a month after Kennedy was assassinated in Dallas. It would be crass to say Superman would stay safe, and even more tasteless to wonder if there was a Kryptonian on the grassy knoll. So I apologize for bring these ideas up, just as DC apologized in its letters column (Action #312).