I assumed it had something to do with the mother either telling him to be careful or he'd get run over by one of those "god-awful automobiles" and that she'll b

I assumed it had something to do with the mother either telling him to be careful or he'd get run over by one of those "god-awful automobiles" and that she'll be pleased that she was right, or maybe slightly less likely that his mother hated him and will be happy that he's dead.