Abu Huraira reported Allaah’s Messenger (sallAllaahu alayhi wa sallam) as saying: By Him in Whose Hand is my life, a time would come when the murderer would not know why he has committed the murder, and the victim would not know why he has been killed.

Hadeeth-Number-6950:http://www.sahihmuslim.com/sps/smm/sahihmuslim.cfm?scn=dspchaptersfull&BookID=41&ChapterID=1211