deputies filmed chasing ` horse thief ' francis pusok in the california desert .
pusok , 30 , falls off horse ; seconds later , two officers stun him with tasers .
they then kick him in crotch and head repeatedly , before others join them .
footage captured by nbc helicopter on thursday , sparked outrage online .
man 's lawyer said it was ` as bad , if not worse ' than rodney king 's beating .
now , 10 deputies have been placed on paid administrative leave by sheriff .
international and criminal investigations are ongoing ; deputies not named .
pusok 's girlfriend of 13 years said that she ` could n't believe ' graphic video .