LPG Hot Water tank pop-off valve erupted - is this normal?

Here are a few things to check. I'm sure others will speak up also:

1. The pressure relief valve has malfunctioned and is releasing at too low a temperature. I'd change this out because it's cheap, easy and can be found at most hardware stores.
2. Thermocouple malfunction.
3. Shut off circuitry malfunction.