random attacker; slasher; street assailant
Refers to a person who attacks strangers at random, often in public places. Commonly used in news reports and crime contexts.
Last night there was an incident where someone was stabbed by a random attacker in front of the station.
Random street attacks are increasing.
passing demon; demon that brings misfortune to passersby
Original folkloric meaning: a demon or evil spirit that brings calamity to houses or people it passes. Now largely historical or literary.
Originally, 通り魔 referred to a demon that brought misfortune to houses it passed by.
Akihabara massacre (June 8, 2008)
Compound of 通り (passing) and 魔 (demon, evil spirit). Originally a folkloric term for a malevolent spirit that caused harm to those it passed; the modern sense of 'random attacker' developed from the idea of an unpredictable, passing threat.