My guess as to what happened would be:
The man realized something was burning, pulled over, grabbed an extinguisher and went out to put out the fire thinking it was minor. When the extinguisher didn't put it out, he got scared. When he ran back into the RV, he told the girls to get out, grabbed the 2nd extinguisher and went back out. The girls were afraid to go with him out the front door through the smoke, etc. and went back to the rear of the RV. Those windows are small and high up and the girls likely had trouble getting out on their own. Once the other folks showed up to help, they were able to get out quickly. The man likely thought that by using the 2nd extinguisher, he was giving the girls more time to get out the window.
I love that my clipper has the two cab doors, the house door at the back, plus the escape hatch over the cabover. But, I have wondered how difficult it would be to get off the roof by the front end. Maybe one of those fire ladders would be a good idea to have on hand. They're made to hook over a windowsill (would work on the roof rail also) for those high up RV windows. Keep it stored as close as possible to the emergency window.