Jeffrey Dahmer was one of America’s most notorious serial killers, murdering and dismembering 17 young men and boys. In some cases Dahmer ate parts of their bodies. In 1994, Dahmer himself was murdered while in prison.

A new documentary,”The Jeffrey Dahmer Files,” explores how a seemingly normal person becames a serial killer. The film features an interview with one of the lead detectives on the case, Patrick Kennedy and his chilling experience uncovering details during the investigation.

This morning, now-retired Detective Kennedy and director Chris James Thompson join “Starting Point” to discuss the new documentary.

Kennedy, who served the Milwaukee Police Department for 21 years, says he had “seen many shootings and many dismemberments and some gory things” but what he uncovered at Dahmer’s home was truly surreal. He recalls being there to arrest Dahmer and feeling an “overwhelming irrational fear” even though he knew he was not in any danger.

Thompson grew up in Milwaukee, and says he remembers people in his neighborhood discussing the serial killings of Jeffrey Dahmer as if it were “a flood or a hurricane…it was a disaster that affected a lot of people.” He adds that in other places like Madison people discussed the killings as if “it was a movie that was coming out next Friday night.”

Ultimately Thompson says his curiosity of how the Dahmer case affected people over a period of time led him to make his film. He says taking a look back 20 years later for those closely involved in the case like Kennedy, the medical examiner and others gives them “some 20/20” to see how it affected them over the years.