PEOPLE editors and experts talk about why they focused on the Long Island Serial Killer case for the new show People Magazine Investigates

No one knew that when Shannan Gilbert went missing, the search for her would uncover at least 10 more dead bodies in the Gilgo Beach area on Long Island, New York — launching the hunt for a potential serial killer (and as many questions as there are theories to answer them).

It was those twin elements in the case, the surprises and struggles, that made it a perfect fit for the Monday night premiere of PEOPLE’s new true crime series on Investigation Discovery, People Magazine Investigates.

The two-hour special reexamined the case since dubbed the Long Island Serial Killer, and PEOPLE editors and other experts gathered for the People Magazine Investigates After Show to analyze further.

• Watch our new 10-part true crime show, People Magazine Investigates, which airs Mondays (9 p.m. ET) on Investigation Discovery

As PEOPLE’s senior crime editor, Alicia Dennis, explains in an exclusive clip from the after show, “I found this case to be gripping and to be one that started out with … Shannan’s disappearance — and then turned up something that no one expected: all of these bodies that are connected to a serial killer or maybe killers.

“And it just seemed to be something that we needed to do a story about in the way that PEOPLE does stories.”

• Watch the People Magazine Investigates After Show, available now on the new People/Entertainment Weekly Network (PEN). Go to, or download the PEN app on Apple TV, Roku Players, Amazon Fire TV, Xumo, Chromecast, iOS and Android devices

Donnie Eichar, People Magazine Investigates executive producer, says on the after show that the case reminded him of Jack the Ripper.

“The thing with this story is, the deeper you dig in, it just keeps unraveling further and further,” he says in the clip, “and you seem like you’re getting further from the truth.”

Eichar continues, “What I also think is extraordinary is this happened less than 75 miles from Manhattan, and the killer is still loose.”

People Magazine Investigates airs Mondays (9 p.m. ET) on Investigation Discovery.