‘Thou shalt not kill“ was a mistranslation. It should be “Thou shall not murder.“or “Do not murder.”
So when Jesus said, "Satan was a murderer from the beginning" the person with intelligence will see that Satan "in the beginning" didn't kill anyone. In the beginning Satan beguiled Adam and Eve into defying the command of God, death , a curse, being the consequence which caused their separation from God and expulsion from paradise into the wilderness where they lived out the rest of their days insane, the sweat of their brow, thinking, producing only thorns and thistles.