This behavior is called "the knockout game" and is practiced by young males is some mainland cities as a sort of perverted rite of passage.  In recent years, in New York City to name just one locale, Orthodox Jews seem to be targeted more than just random chance would lead one to expect.

That death can result from a single punch is something people who grew up in an earlier era should reflect upon before waxing nostalgic about past schoolyard fistfights and barroom brawls.  Personally, I don't feel striking anybody is justifiable unless it's to ward off an attack or in rare instances, to prevent a person from harming himself.