So normal stuff, then?

I argue that by the time an extinguisher was used, the burns are fatal. Indeed, a standard chemical extinguisher could kill him all by itself.

I wonder how long the response from a fire truck may be?

I realize it's mind boggling to realize that people suck, but most of the time it just doesn't matter. Sure, it absolutely can, sometimes, but how often do people even realize that the thing they're witnessing isn't just an act?

Is the first thing you think of when you stumble upon a burning human "oh, that dude is in need of assistance", or more like "what the fuck is this"?

I don't know what I would do, personally, having never been in the situation, but I'm not at all surprised that normal people behave like normal people.