In 2005 in the United Kingdom, BBC News reported on the happy slapping incidents, in which the attacks were filmed for the purpose of posting online. Local teens said that the object is to render an unsuspecting target unconscious with a single punch, and, if the assailant does not succeed, his companions will turn on him instead. Raustein was stabbed after falling to the ground.

In September 1992, Norwegian exchange student Yngve Raustein was killed by three teenagers who-according to Cambridge, Massachusetts, prosecutors-were playing a game called 'knockout'. See also: Murder of Yngve Raustein and Happy slapping Before 1992, the act of attacking and trying to 'knock out' a citizen for entertainment also existed and was given different names, such as 'wilding' or 'One-Hitter Quitter' in the late 1980s and early 1990s. The 'Knockout game' became known after the murder of Yngve Raustein in 1992. Some news sources report that there was an escalation of such attacks in late 2013, and, in some cases, the attacker was charged with a hate crime. Serious injuries and even deaths have been attributed to the knockout game. Other names given to assaults of this type include ' knockout', ' knockout king', ' point 'em out, knock 'em out', and ' polar-bearing' or ' polar-bear hunting' (called such when the victim is white and the assailants are black). The assaults have similarities to the happy slapping trend seen in Europe, in which camera phones are used to record assaults. ' Knockout game' is one of the names given in the United States for assaults in which a person (with others acting as accomplices or lookouts) attempts to make an unsuspecting victim lose consciousness with a single sucker punch. For other uses, see Knockout game (disambiguation). This article is about the form of assault.

Progressive knockout