As a 78-year-old woman walked down the street in Brooklyn, carrying her purse and bags, a young black male, about 20 years old, punched her in the head as hard as he could and ran away. The man said nothing and didn’t steal a single item.This is one of the latest instances of “Knockout,” a “game” of evidently increasing popularity. Young people — sometimes female but usually male, predominantly black, in their teens to early 20s, in groups or alone — approach unsuspecting strangers and punch them in the head as hard as possible with the intention to knock them...