My theory is that they burned the RAV4 and went briefly into Sundance on foot to grab a boat and travel down Sundance Creek to the Nelson, then traveled some distance down the Nelson River to before the rapids and pulled to shore.
They took the gun but no other gear and pushed the boat back into the river where it went over the Limestone Rapids and spilled all the personal items and badly damaged the boat. These items washed up at various points downstream. It's the same pattern of destroying both their conveyance and all the gear in it, for the third and final time.
They scrambled up the sandy cliffs leaving a clear trail for LE to find once LE began looking for it. They beat their way 1 km into the bush and put the gun to work, leaving both dead.