I have a special breed of vampires. They are, like any vampire, dependent of human blood and they need to consume it every few days in order to stay active. If they don't, they go into coma, and eventually die. They are weaker than people of the same size and they don't have any special power, except for their heightened senses (sight, smell, hearing). They mostly like to act at night, as the sun light affects them.
The question is how would they get their blood without raising suspicion? They could start a blood bank, and some blood could magically disappear. They could also start a morgue, or a funeral home and use the blood from the bodies of deceased people.
But, they also have rituals for bringing back some older deceased vampires and they need fresh warm blood. How could they setup a police-proof scheme for kidnapping people and sacrificing them in their rituals?