By the way, Reggie, in black folklore "night riders" were not exactly vampires, but white folks, particularly KKK members. The KKK used their white sheets partly to scare blacks into thinking they were ghosts, but most blacks knew exactly what they were. See Glady's-Marie Fry's book Night Riders in Black Folk History.

One of the rumors about night riders was that they preyed upon blacks to use their bodies in medical experiments and as cadavers in medical schools, sort of like Burke and Hare and Doctor Knox rolled into one! These particular night riders were also often known as "night doctors" or "Klan doctors." This belief might be behind your friend's vampire interpretation.