Would you shoot your commanding officer in defense of your own humanity?

Your C/O order you to round up 1000 villagers and line them up, old men, young boys, women and children and oders them to be shot. If you don't shoot them, you will be disobeying orders and may be shot yourself. If you turn the gun against your C/O, your squad may turn against you and you may not save the villagers or yourself but you would have died as a decent human and not a murdere.