Generally speaking, in cases like this, you have to actually physically intervene to stop the genocide. They're using machettes and other primitive means to do much of the killing, as in other genocide cases in very poor nations (like Rwanda or Cambodia). Sanctions are never enough against what are already extraordinarily poor nations (we've sanctioned North Korea for decades, as much as any nation can be, and they're proceeding apace with ICBM nukes).

The question of stopping this kind of genocide is primarily: who is going to militarily intervene and in what manner.