It was a totally unprovoked attack on an innocent man.
那完全是对一名无辜男子的无端袭击。
Examples from the Corpus
unprovoked• Troops have been accused of unprovokedaggression against innocentcivilians.• But if they were used only after proper training and in self-defence, how can that be construed as unprovoked aggression?• It was a totally unprovoked attack and in the end the police were prosecuted for assault.• The unprovoked attack has left the man critically ill in hospital.• A man died in an apparently unprovoked attack in centralOxford last night.• Any Rottweiler that makes an unprovoked attack on a human being should be destroyed.• Yildiz was killed on the streets of Glasgow last weekend in what is thought to have been an unprovokedracist attack.