String him up in a town square, noose around his neck, feet on a chair but just barely. Sell rocks in varying sizes to people who want to participate in the following (with proceeds going to the victim's family). Those who purchase the stones can lob them at the psycho or the chair. Either continue until the asshole dies from being stoned to death or the chair topples and it snaps his no-good neck.

Alternative: bring back the guillotine. Execute him in a stadium and sell tickets, proceeds going to the victim's family. Everyone else can watch it on TV.