Briefly.
It may have been pre-ordained they were going to die. Don't know of any mass suicides by impromptu fire. I suspect Jonestown would have had a different outcome if folks were asked to throw themselves into a fire.
And, the FBI should have had, just to cover it's ass, some fire suppressant equipment around. I know, the could have shot at the firemen. Hoses could have been run up behind the tanks.
Or not. It they would have had them there, and decided to not use them, that would indicate something other than not having any ability to suppress a fire.
Arf