Exodus 20:13

Hebrew רצח, not simply "kill" or "murder," but rather "to dash to pieces". Compare the context of Deuteronomy 22:6, "ורצחו נפשׁ" and he is breaking the soul/breath to pieces..." Psalm 62:3, "תרצחו כלכם כקיר" "you are all being dashed to pieces like a wall..." and Psalm 42:10, "ברצח בעצמותי" within the breaking down of the bones of myself..."

Often "blood" is found in the context of this verb "dashing to pieces". But "blood" itself is not merely blood of the flesh but quite a bit more: 

"only flesh with the soul/breath of himself, the blood of himself..." (Genesis 9:3 RBT)

 "For the soul/breath of the Flesh is within the Blood of Himself..." (Leviticus 17:11 RBT)

Thus this word seems to have more to do with "killing the soul" or "murdering the soul" as it were, a concept discussed by Jesus in the New Testament.