Andrews was captured alive by the Legion was brought back to the Fort. Now he fights in the the arena. Before the Courier arrives he has already been challenged once and survived.[1]
Xbox 360 When exiting Caesar's Tent after killing Andrews in the arena, his corpse may launch hundreds of feet up out of the arena and come crashing down somewhere nearby.
References
↑The Courier: "I'd like to fight in the arena." Otho: "There's a captured NCR trooper available - Sergeant Andrews. He's already been challenged once and survived, so he should be a worthy opponent." (Otho's dialogue)