>> bram van der meer: you would expect maybe that a very bad person did this, a person with-- i wouldr knows psychopathic minds. he had been an investigative psychologist with the national police force in the netherlands. on vince pankoke's team, he analyzed the behavior and mindsets of suspects they were considering. that's your first instinct? so, it had to be a psychopath to do this? >> van der meer: yeah. but you have to be so very careful. it's war. you're surviving. your day-to-day life is filled with fear. your family might be arrested the next day. you're thinking everyday about your own survival. so, that's the context. >> wertheim: in a vacuum, it had to be a psychopath to do this. but given the context-- >> van der meer: that's right. >> wertheim: then what kind of person might do this? >> van der meer: yeah, and then-- and then you end up in-- in a situation where it could be anybody. >> wertheim: over time, their focus shifted to someone who, on the surface, might not have raised suspicions. this suspect wasn't a neighbor of the franks and didn't work for them, but the f.