Boothill didn't really want to leave Mei's side once he noticed that the goblin continued to essentially half-ass its punches once he had gotten his arm torn off and thrown off somewhere. But, while his body hurriedly does some emergency shut downs to stop the leaking of vital fluids, he will dash towards the rear of the goblin and hold out his left arm the hole in his hand unloads into a muzzle of another gun. That's right, his left arm is also a gun.

"Shoulda aimed for heart, fudgehead."

It only takes a couple shots, but the hatch is blown off and the ruby inside shattered.