The problem with anything other than the death penalty is that some future president might pardon the guy.
(Remember Jimmy Carter pardoning the Puerto Rican nationalists who took pot shots inside Congress?...After Carter pardoned them they returned to Puerto Rico to a standing ovation at the airport.)
Ref: https://en.wikipedia.org/wiki/1954_United_States_Capitol_shooting
I don’t know but I would think state would be different then federal but I guess a future Utah governor could pardon. I don’t remember the Carter pardon. We did a tour with our congressman and he pointed out the damage they made in Congress. Also got to see the silver ink well that’s on the desk when congress is in session.