I always hate hearing something like this... especially when someone is injured. On campus settings like MSU ....in most cases we have multiple boilers in every building from domestic hot water, heating and supplying steam to labs and other processes. We even have a powerplant operation that supplies 100lbs of steam to half the campus. We have about a mile of underground steam piping in tunnel systems.
Just speculating but either a solenoid operated gas valve failed to close on mis-fire and filled the boiler up with gas...then tried to re-light or it was a steam explosion when relief valves , low water cut off or high limit switches failed. Its hard to believe all three safety devices failed to cause a steam explosion.
I'll also say all three devices are required in Kentucky on every boiler for the steam side and redundant solenoid gas valves are reccommended in most applications. I cant say thats the same requirement for Tennessee. Their plumbing & mechanical codes alway seemed pretty lax in comparison to Kentuckys. I'd say that they will be investigating this from several agencies to see what happened.