Character studies are  common in literary fictional genres, and they also have a role in non-fiction. While it is true that the characters are “real” people, it is also true that they are being presented to advance a narrative. They’re present for a reason, so the author needs to make them as round (multifaceted the way people are) as possible. The people need to be described, they need dialog, they need to be presented from a point of view, etc.
It is clear by page 95 that Cullen is a serial killer and is using his position as a nurse to identify victims. However, it is also clear that there are other signs that he exploits and victimizes. 
Rather than using the Department of Justice definitions for victim, I want to use the definition provided by the Oxford Dictionary of English:
“noun a person harmed , injured , or killed as a result of a crime , accident , or other event oraction [emphasis added] : victims of domestic violence | earthquake victims .
¢ a person who is tricked or duped: the victim of a hoax .
¢ a person who has come to feel helpless and passive in the face of misfortune or ill-treatment: I saw myself as a victim | [as modifier] a victim mentality .
¢ a living creature killed as a religious sacrifice: sacrificial victims for the ritual festivals .”
Please tell us about your reactions to The Good Nurse so far. Specifically, do you see evidence, other than human homicide, of abuse, exploitation, enabling, etc., taking place in Cullen’s interpersonal relationships and behaviors in these first 95 pages, and if so, what do you conclude about the context in which these homicides happened? Add any additional points you find important: there are many ways to address this text.