Suicide by gun shop
Yep. Dude had a death wish.
That is more common than you think. Only the usual M.O. is for a suicidal person to go to a range, rent a gun, then shoot themselves.
Here in Michigan we had a person who rented a gun at a local shooting range, then left with the gun and shot his ex-girlfriend dead at her place of work, then shot himself. The range never even realized the gun was missing.
Amazingly, that gun range hasn't been sued out of existence yet. This was three years ago, and I believe that there may be one lawsuit still pending, so it may happen yet.