i guess that covers "lesser measures" and "immediate danger" 
So the SWAT Team, surrounding the cabin, behind total armor, with the ability to shoot while fully protected by armor, were under immediate and significant danger of serious bodily injury or death, and the supposed use of a single canister of traditional gas had exhausted "all lesser means"?
There is no question, the argument will be that the incendiary devices were intended to provide "lesser means", and the fire was an unfortunate accident.