"Thou shalt not commit murder." is the correct translation.
If you read the Old Testament when the Ten Commandments were either written or "revealed," depending on your point of view, there was one hell of a lot of killing either sanctioned by, ordered by, or actually committed by God Himself. Wars, executions, grisly deaths, and outright massacres. Reading the Old Testament cover to cover starts to make you think God was walking around wearing a hockey mask before, like many others, he had a kid and it mellowed him out.
Obviously, even if the translation was not available, the commandment does not refer to killing in general.