I lean toward Chad's idea.

Did you hear a loud pop sound at the time this happened ?

What pin(s) were the resistors that cratered connected to on the tube?

I have an ASL AQ1003DT AMP which was connected to a pair of Klipsch KLF30s and had an EL34 short out. It sounded exactly like the sound of my wife stepping outside and "closing" the door after discovering the trifling cost of some of my audio upgrades

Thankfully we have a motorhome !