Angel Blood. The Ryan Chronicles, #4

Someone is murdering people, draining them dry, and the police suspect it may be a vampire. When the captain of the York police department turns to Tom Ryan and his paranormal investigation agency for help, Tom takes one look at the crime scene photos and knows the killer isn't a blood sucker. Tom and his business partner compare the murders with a list of angel descendants and a chilling pattern is confirmed.
Angel bloodlines are being extinguished, and there are only a handful left between the killer's hunting ground and their family in York. They must stop the assassin before he can cross off any more names on his hit list.