During Showdown, all shots that hit enemies ricochet towards other nearby enemies, dealing 10% weapon damage per hit. Additionally, Showdown ending triggers an explosion on all enemies who have been shot by you during Showdown.
Ricocheted Bullet Damage: 10% weapon damage per hit
Under the fact that the enemies "explode", it should be understood that they are being dealt a big explosive damage, which is fatal for most.
Since getting crippled during Showdown is also treated as it ends, the explosion will trigger at the beginning of the crippling, which may almost instantly grant a second wind if made a kill.