At last. Proof enough that the thing he'd been tailing for days was a vampire. Proof enough for Abraham to strike . He had to admit, though, this one had guts, dragging a girl like that in to an alley at this time of day. The tattoo on his neck had greatly increased his suspicion, but only an attack could provide proper evidence and opportunity. 

By now he was poised on the rooftop above, waiting for the moment that he had a clear shot, when the girl would be too weak to fight and get in his way. Once his moment arrived, the action was almost a reflex. Flicking the knife through the air, towards the back of his neck before leaping off the roof, weapon firmly in his hand to kill the attacker with. 

The girl was almost a second thought, kill first and deal with the victim afterwards. Knowing that she would ask questions about the attacker or about his method, it was best to ignore them until the creature was dead and he was sure they were safe. With his knife lodged in the back of the creature's neck, and another planted firmly in to it's chest with a snarl, he held firm, not looking at the girl until it stopped twitching, keeping his hood and scarf firmly up to hide his face from anyone watching. Abraham could then push the body aside, and focus on the victim, a young girl, from the university, most likely.
"Are you bleeding?" He asked, not moving anything away from his face in an attempt to uphold his anonymity.