Murder is NOT legal.
If you do not like the law, CHANGE IT! If you take the law into your own hands like this fool, expect to suffer the consequences.
Please, GET A GRIP ON REALITY - shooting someone multiple times (in a church!) until they are dead is murder.
Pity it appears that he will only receive a life sentence.
So was the extermination of Jews by the nazis.
However, there is a higher law that we all must obey; we may avoid prosecution for a time, but justice is certain.
I agree that shooting the monster in a church was plain wrong, and it left him no defense. If he had shot him on the way into his clinic, a manslaughter to prevent murder defense might well have held.