But as long as he is alive he IS in position to harm me or my family.
He will get out of jail someday, and may come looking for me or mine. The only way to zero out his threat potential is to zero HIM out.
He was convicted of murder you littler boy.
Did you know the kid had a family? They are now a threat to you, if they think like you do.
If somebody breaks into your house and you kill them, you should probably wipe out their family, including the baby, just in case.