I think they are on foot (and won't get far), but I'm also considering another vehicle.
They might have stolen one before they arrived in Gillam, with each perp driving a different vehicle into Gillam. They ditch and burn the Rav4 and then depart in their "new" stolen car. At the time they were in Gillam, nobody was looking for that car or knew they were perps (and if they arrived in separate cars, they weren't noticeable as a duo).
As someone mentioned upthread, if they murdered and stole a vehicle from tourists on vacation, it's possible a vehicle hasn't been reported as stolen and people aren't yet reported as missing. It's such a vast area, there could be people on the side of the road that no one has noticed yet.
![Frown :( :(](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
I hate that thought.
I lean toward them being on foot mainly because it seems like LE thinks they are still in Gillam and because I hate the thought of them having killed someone else for a car and because they haven't been spotted as a gas station (though I suppose they could just steal another car when they run out of gas).
I've been wondering if they were trying to drive the Rav4 off road and it got stuck, so they abandoned it on the spot.
jmo