The Night Hunters
Steve's first client was a woman who believed that she was being stalked by a demon, waking up with only the memories of great fear and constant lethargy. She even went the whole nine yards, getting a priest to do an exorcism, putting crosses everywhere, horseshoes over doorways, dreamcatchers, etc. Eventually, Steve was able to find out that it was not a demon stalking her, but a vampire who was able to cause great fear in people, sometimes so much so that they would go unconscious and lose all memory of the encounter. It would break into her house, scare her unconscious, drink from her, and then come back every few days to do it again.
Fortunately, Steve had other plans.
Note that Steve didn't actually learn a whole lot about vampires from this encounter other then that vampires exist, which he probably already had an inkling of from his Angelic duties as an information gatherer. He learned that they can induce fear in people, and that they don't appreciate hair-spray and lighter torches in the face. He has no idea what a Nosferatu is, how vampiric society works, or about "Disciplines".