The first 'reported' isn't the same as 'first happening'. The knockout game is one more reason to hate liberal elites... they kept the lid on this horror to protect votes for democrats.
My guess... just a guess, YMMV... stuff like this probably has been going on since rowdies got too much ale in pre-revolutionary America. For which they’d be whipped at the whipping post or something like that. But little of it tied to racial tensions until modern times.