This young man has grown up in a dangerous neighborhood in which violence is a fact of life. This is a neighborhood and a family that was and is always on the precipice of disaster. This is the kind of environment that when coupled with a pre-existing propensity, creates the kind of psychopaths we have nightmares about. Coupled with the temporary absence of an older brother (apparently away at war at the time) at the time of the sudden and messy suicide of their mother, the main character of the film who found her immediately after the act-- a young teen is essentially turned into a locked and loaded weapon.
It's also apparent that the disturbed young man is in court-ordered counseling ("You know you aren't allowed to cut our sessions short"), for killing and mutilating animals and his fascination for blood and violence is known--but what most of the viewers here seem to miss, is that this significant and formative experience is what formed his fascination for vampires and compulsion to drink blood and not the other way around. Even without this knowledge being spoonfed to the audience, it is clear that he is "different"-- perhaps always different (perhaps even on the autistic spectrum) and his difference is recognized by others ("Freak!") given his inability to connect with others, and his lack of emotional reaction to even the roughest abuse (what is called a flat "affect")--but what no one knows is that his fantasies are not solely inside his imagination.
His big brother--now his sole source of support, is in turn being crushed by his own problems; the effect of their mother's suicide (their mother's bedroom is closed off and unoccupied, even as he sleeps on the couch because his little brother occupies the only other bedroom), depression, fatalism, his brother's severe issues and apparently PTSD; he isn't a psychopath, but death isn't a stranger-- and he knows he isn't able to do anything for his psychopathic little brother, except accept him as he is "no matter what happens, what he has to do to survive".....He is saddened that he can't protect his little brother; not from his violent "freinds" who threaten the neighborhood (though he no longer hangs with the gang himself), and he cannot even protect his little brother from himself--clearly he has accepted that his little brother is going to come to a bad end--but he does what he ca; given as little as that might be under the weight of his world, he still obviously loves his little brother.
This is quite a different vampire film in that the protagonist is not actually a vampire. His thirst for blood is quite real, but his compulsion to kill may be more of convenience given he seems to gain no satisfaction from the act, and in fact demonstrates a modicum of remorse--moreover, his remorse directly leads to his final acts of-- if not "redemption" in the traditional sense, in a way that at least gives his life some sort of meaning (which I won't give away) in the limited world he inhabits.
It's the blood that calls him--not the act of obtaining it-- which his physical being in fact rejects (and dare I say, his rudimentary conscience as well, that glimmer of humanity he in fact does possess behind his blank uncaring mask?); but like many serial killers, even at his young age he is trapped within the ritual he has created in an effort to control his impulses. He knows he is bound, though we don't know if he is bound by rules only his imagination has conjured, but like the best of stories, he sticks to the rules he has bound himself too--both good and bad.
This is truly a unique take on the vampire story, with very detailed and nuanced characters.