“And cheap too.
You can even re purpose a gas chamber”
Another option is an altitude chamber. At 40,000’ you have 3-5 seconds of useful consciousness and you don’t feel anything. No altitude chamber available? Surely the state has an airplane. Put the pilots on oxygen, take it to 35,000’ or so, fly around for 15 minutes and land - the deed is done.
Treat him like an innocent baby and abort him in safe, legal, and rare fashion.
Take him up on an Alaska Airlines plane and have him sit next to the door...