Not sure which gang uses 3 fingers. The camera man shows off 3 fingers and mutters something. Also not sure if the video is from Mexico, or Brazil. But it is likely from either.
In the video, a presumed rival is on the floor, maybe pretending to sleep. He gets chopped in the back of his neck and his back a couple times with a machete. He slips on his own blood trying to get away. Eventually, he is finished off with a shotgun blast and a gun.
Props to Best Gore member @seraphim-serenata for the video: