bystander [bystanders](a person who, although present at some event, does not take part in it; an observer or spectator) noun [UK: ˈbaɪ.stæn.də(r)] [US: ˈbaɪ.ˌstæn.dər]The terrorist sprayed bystanders with bullets. = El terrorista acribilló a balazos a los transeúntes.
passer-by(a person who is passing by) noun [UK: ˌpɑː.sə ˈbaɪ] [US: ˌpæ.sə ˈbaɪ]