Who is Hit men from The Husband and what is their importance?

Campbell's hit men are assigned the job of taking with Mitch to the desert and doing away with him. Mitch correctly assumes they are experienced and comfortable with their job. He is grabbed, stuffed into a trunk, and driven to the desert. What the two men haven't counted on, however, is the fact that Mitch has hidden a gun on his ankle. So when they open the trunk, Mitch pulls his gun, kills one of the men, and wounds the other.