I must be missing where the grenade was thrown, even when enlarged and on slow motion.
If it wasn't a grenade then... I guess troops planted a bomb, waited until a dog sniffed at it and then initiated the explosion?
That video could have just as easily been labeled "Troops stop convoy to investigate suspicious roadside object that explodes when disturbed." Given the contempt with which canines are held in that part of the world, it wouldn't surprise me at all if it were tripped remotely by someone disappointed that his little present wasn't nearly as well disguised as he had hoped.