1) Only God determines what is murder and what is the taking of live. God is the giver of life and he alone can take it at His will. We cannot place our moral system on him and say that anytime to take a life is wrong. We cant do that. He decides if someone should die.
So these instances where God condmened murder shows us that there is justice by not letting wanton killing occur. But when He allows killing to take place by ordering it, it is also justice.