there is no specificity, he didn't say "don't kill people you don't like" he didn't say "don't kill people" it says "thou shalt not kill"
everything you eat was once alive and is now dead whether by your own hand or the hand of another
if you refuse to eat you would die and in essence have killed yourself
it's always bothered me
\- Brave AI
The English language has changed a lot over the years, without any expertise in the older versions I'd take a wild guess and say the older text refers to what we today call "murder", basically killing with intent, for no valid reason.
Self defense if unprovoked must be allowed. If you kill someone while defending yourself it's usually accidental, if we're looking back to the old days before deadly weapons such as firearms. Hence no intent.