"We both got goosebumps all over our body. We knew it was her van as soon as the footage passed by it," Bethune told ABC News. Watch a preview of Bethune's interview on Friday's episode of ABC's "20/20" about the Petito case in the player above.
"Life on Line: The Last Days of Gabby Petito" reports on the horror that unfolded in Wyoming's Grand Teton National Park and the details that lead to the discovery of remains identified as Brian Laundrie, Petito's boyfriend.
Through interviews with Jim Winder -- who is the former Moab, Utah, police chief -- experts on body language, and legal analysts, the show will break down the viral body camera footage from the couple's police stop in Moab days before Petito disappeared.
TIMELINE: Everything we know about Gabby Petito's disappearance
In addition to travel blogger Bethune, the show includes interviews with:
- Miranda Baker, a young woman who gave a hitchhiking Laundrie a ride in Wyoming
- Jason Jensen, a private investigator and co-founder of the Cold Case Coalition who searched Grand Teton National Park with his cadaver dog
- Mykel Hawke, a retired special forces combat veteran and survival expert who takes "20/20" cameras through the dangerous swamps of the Carlton Reserve in Florida, where authorities found Laundrie's body.
The episode also discusses calls for attention to similar missing person cases involving people of color and indigenous women who have disappeared in the same area as Petito.
"Life on Line: The Last Days of Gabby Petito" is available to stream on Hulu.