She picked him up on August 29, four days after the last time Gabby Petito is known to have called her family.
Laundrie told Miranda Baker he had been camping alone while Gabby Petito worked on their social media page in their van.
He eventually got out of Baker's car when she said she was heading to Jackson Hole.
"He got out, and you know, he was thankful and he was kind of in a hurry. He said he was going to go across the street into the parking lot and find someone else to give him a ride, but, when we looked back 10 or 15 seconds after he got out of the vehicle he was just gone," she said.
You can watch the entire exclusive interview with Baker on "Good Morning America," beginning at 7 a.m.
The FBI confirmed that a body matching Petito's was found in Grand Teton National Park in Wyoming on Sunday night.
FBI says Body matching description of Gabby Petito found in Grand Teton
The Laundrie family attorney released a statement on Sunday night saying "The news about Gabby Petito is heartbreaking. The Laundrie family prays for Gabby and her family."
Laundrie remains missing, last seen by his family in Florida last week.
WATCH | Chopper hovers over police search for Brian Laundrie at Carlton Reserve
Video: Police search for Brian Laundrie continues in Carlton reserve
RELATED | Gabby Petito disappearance timeline: What we know so far
MORE: Police body cam video shows Gabby Petito, boyfriend after 911 call
Police release body cam video of intereaction with Petito, Laundrie
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