The former investigator who helped catch serial killer John Wayne Gacy says most violent predators don't seem dangerous

• A former investigator who helped catch John Wayne Gacy said not all serial predators seem evil.
• Mike Albrecht told Insider that Gacy, who killed 33 people, was "was basically your guy next door."
• He also said serial predators "don't walk around and have horns on their head or this evil look."

A former police officer who helped apprehend notorious serial killer John Wayne Gacy said that not all violent predators appear outwardly evil.

"These people - John Gacy and other mass murders, or predators, or sexual predators, or whatever they may be - they don't walk around and have horns on their head, or this evil look on their face all the time that would scare anybody away," retired investigator Michael Albrecht told Insider.

Albrecht, who worked in law enforcement for 45 years and is featured in a new Peacock true-crime series about the murders, said that Gacy appeared ordinary to many of the people he encountered.

"I mean, he was basically your guy next door... he was very well-liked and respected," Albrecht said. "You know, people think of John Gacy as this big, evil, mean person that had to be scary - but it wasn't like that at all."

Albrecht worked for the Des Plaines police department, and was assigned to surveil Gacy after he was suspected of being involved in the 1978 disappearance of a young boy named Robert Piest.

During his time watching Gacy, Albrecht had frequent conversations with the serial killer and even shared meals with him at local restaurants and bars.

The scope of Gacy's crimes - he was found guilty of sexually assaulting and murdering 33 young men and boys - as well as the efforts of law enforcement to catch him are detailed in Peacock's upcoming series "John Wayne Gacy: The Devil in Disguise."

Ultimately, Albrecht and his colleagues were able to arrest Gacy, and uncovered the bodies of many of his victims in a crawlspace underneath Gacy's Illinois home. Gacy was subsequently convicted of murder and executed in 1994.

But Albrecht reiterated that Gacy, as well as other violent criminals, aren't always easy to recognize in day-to-day life.

"You can't be suspicious of everybody that you come in contact with, in your life, but you can't be easy going, blasé about it either," Albrecht told Insider. "You're dealing with humans. Humans are not perfect by any means."

"John Gacy - as far as I'm concerned, in no way was he insane," the former investigator continued. "He was very plotting. And what he did, he was methodical with what he did."

"John Wayne Gacy: The Devil in Disguise" premieres March 25 on NBC's Peacock streaming service. You can watch the trailer below.