This is what I would do:
Give him a trial. Present the best of the evidence against him. It should not take more than a week to arrange it and a week for the trial. Then, immediately after the trial he would be taken out and shot. His body would be burned and his ashes scattered over the sea. There would be no funeral. Anybody who dared to hold a memorial service for him would get sprayed with 20 mm cannon shells at the rate of 100 per second as a method of discouragement.
David F Mayer