Cadillac CTS 2dr Rear window Explosion (no pic)

Wondering what would cause this to happen.

Quick run down:
Lady at work gets into her 2011 Cadillac CTS 2dr. Its 50degrees and raining. She starts the car after closing the door. The rear window then explodes with a 2ft wide 1ft high/tall hole in the middle.

What could cause this?

One thought I had, trying to figure out if it can be true… When she turned on the car, it sent an extremely high amount of electricity through the rear defrosters causing some type of explosion to occur.

I have never seen or heard of this happening.

An object go threw it?

*through

sometimes just internal stresses or imperfections in the glass are compounded by thermal stresses or other chassis stresses and can cause a propagation of the imperfection.

yea…bb gun?

Was there a bowling ball in the back seat?

This was my first thought.

Would make a lot of sense, especially with tempered glass.

no bb’s or bowling ball, nothing.

sniper rifle

Maybe she farted?

nickleback set on blast

Bad bad girlfriend.

We all only hoped that was the case. lol