passer-by
noun [ C ] uk/ˌpɑː.səˈbaɪ/ us/ˌpæs.ɚˈbaɪ/ passers-by
（尤指在不寻常之事发生时经过某处的）过路人，行人
someone who is going past a particular place, especially when something unusual happens
The gunmen opened fire, killing a policeman and a passer-by. 持枪者开枪打死了一名警察和一位路人。