It's not dead. It just got too hot or the pressure got too great.
I'm no expert on this, so wait for the pros to tell you why this happened.
But, I'll put in my 2 cents anyway. If you have a check valve or a pressure reduction valve, they could be malfunctioning, causing a build-up of pressure. Too much city pressure or well pump pressure could also cause the T&P valve to pop. If the problem is due to excessive pressure, The "cure" is usually to install a PRV and an expansion tank.
I would dial the temp. down first and see if it happens again. Could be just a one-time thing. If your temp. doesn't get any colder, then one of your thermostats is bad.
PS: Solsacre makes a good point, you should have a pipe attached to the T&P valve that leads to a floor drain, so you don't get all flooded out.