Thou shall not kill is rendered incorrectly. In the original Hebrew, it is stated as thou shalt not murder, which is a huge difference. If it was only about killing, then any required burnt offerings at the time would been contradictory to the commandment. Also, this is the reason for the seven cities of refuge, in the event of an accidental death. These cities were named as such, NOT to protect the accidental slayer but to keep the families from murdering in revenge and thus keep them from violating the commandment.