I bumped into the fire department squad

At first, from a further distance, i thought maybe it was a house on fire but at closer inspection it was actually a shed. And so I asked someone that was observing and he told me there was a loud bang, possibly a propane tank but how did it explode?

Those tanks don't just explode on their own randomly, and i don't think someone was cooking a steak in -15 windchill weather but you never know. But whatever the case may be i hope no one was seriously injured.