Truck fire i77 OH

This will be a bit long winded, please bear with me.

So I was up north in OH around two weeks ago running west on 77 I look over to the ear bound side and see a rig parked on the shoulder fire underneath of it.

I call out on the CB “hey are you a ####### or do you not have a fire extinguisher” he comes back and says “I used it can you help”
It takes me around 10 minutes to get turned back around and pull in behind him. He has already unhooked the trailer but the tire looks like it’s rolling now.

I toss him my extinguisher (a big 20lb bottle) and that knocks the fire off so we can start looking for water to cool it off. We find s bucket and some jugs and cool it down.


I noticed s few things and I’m curious.
I noticed the tire was not actually burning yet, it was axle grease.

the axle grease was BOILING and oozing out, where it had caught fire.

there were no drag marks, or exaggerated tire wear from what I could see.

so here is what I want to know.

Does this sound like s typical brake fire? To me it seems more like bearing failure.