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The final blow to Marlow, when it looks like he and self-infected Eben are evenly matched, Eben punches a hole straight through Marlow's head in a brilliant shower of blood, which makes the other vampires back off and run away.
When Eben injects himself with Billy's (vampire-infected) blood so he can become a Vampire and fight Marlow in order to allow Stella and the girl to safely escape.
Beau absolutely curb-stomping the vampires until he runs out of ammo and commits suicide... which he fails to do. This leads to Marlow crushing his head underfoot.