you are a vampire hunter. You were walking in the forest hunting vampires, you already killed a few, so your basically covered in blood and wounds, but the wounds didn't bother to much, it's nothing you can't handle.

After a while of walking you smelled blood. You quickly, but quietly made your way over to the smell. As you got there, you hide behind a tree and saw a vampire biting someone's neck.

What do you do?