Rhain is a notorious vampire hunter. Even though he's a vampire, he must kill all other vampires to be human again. 

In this world it's fight to the death. If you come across a vampire, especially one that's short tempered you must kill them. 

Rhain was changed by his master that taught him to shoot a gun within a month. 

His master only did night classes which makes Rhain understand why his Master only taught at night.  

That same night after being changed his Master asked Rhain to kill him which Rhain obliged out of anger. 

Now if there is a vampire near, Rhain's gun will start pulsating like a heart beating and automatically refill itself with bullets.

Rhain became feared by all but it's up to you to figure out how his story ends.