Shoot him again.

He's going to bolt." Marcus ran on, firing as he ran.

The mule, one foreleg trailing, scrambled along, squealing and snorting.

Marcus fired his last shot.

The mule pitched forward upon his head, then, rolling sideways, fell upon the canteen, bursting it open and spilling its entire contents into the sand.
Marcus and McTeague ran up, and Marcus snatched the battered canteen from under the reeking, bloody hide.