Well, since I sleep in a single bed, I first will assume the blood has come out from me I will immiediatly check to make sure I didn't, to word it gracefully, bleed from my dick and if it doesn't look bloody, the assume it was my anus that bled and if it did I would go to a doctor, but if my clothes aren't soaked in blood I would know for sure that it didn't come from me, so I would dispose of the sheets and next time I go to sleep lock myself in my room (I'm assuming that if I couldn't even remember what I did I wouldn't be able to properly unlock a door with a key) and set up a video camera, to see if what happened was anything like changing into a monster, if I wake up and there's no blood then I would repeat the experiment the next night and if the only thing I found that was interesting was me just thrashing around violently while sleep walking I would tell the authorities what happened, get something to prevent me from going on sleep walking murderous rampages and most likely be pardoned for being unconscious at the time of the act, although if it turned out what was happening was that I really was turning into a monster... I'd just continue making sure that I couldn't leave my room at night and hope that no more violent incidents occur.