I'm interpreting that to mean there were very strong winds in the area that ripped the shelters up and away, although I could be wrong.
I wonder if they all deployed. I've been a firefighter as well (I'm still red carded, but only as a Resource Advisor). I think the instinct to keep moving would be pretty strong. Absent a clear order from a superior, it would be a hard decision to stop trying to escape and instead go for the shelter - especially if the only place you've got to deploy in is marginal. I've known a few firefighters who swore up and down that they would never deploy, but would somehow always find a way and the energy to keep running.
I can see how with an attitude like that, the instinct to keep moving could get a person in a situation where they never do deploy the shelter, succumbing to scalded lungs and heat without the time to get the shelter out.
For all that most wildland fire fatalities are aircraft or vehicle related, or heart attacks, the burnover is still the nightmare we all have. I can't imagine the fear and panic. I mean, the shelters work, they protect the firefighter from a great majority of the heat, the face down position provides just enough cool air to avoid lung damage. But even then, when deployed when it was really needed, the survivors always had severe burns.
I heard this morning on NPR that the 19 who lost their lives were part of a 20-person team. I can't begin to imagine that kind of survivor's guilt.
It sound as if there were 18 members of the hotshot crew killed, plus one other firefighter. Two of the hotshots survived and are in a hospital. Maybe. It'll take a few days for the news reports to sort out the rumors and incorrect initial reports, just like in any disaster.
ETA: The current news accounts match DragonLady's version. What I heard and referenced in the preceding paragraph does not seem to be right anymore.