Some possible causes of this:
1. GF got pissed off. Tied penis to car, drove off, ripping penis off.
2. GF drove her motor bike over his balls, fast!
3. Alien penis infestation.
4. Really bad gas causing explosion
5. Bad gas, tried to light on fire, explosion
etc. etc. let us know your theories in the comments!
In the case of 1 or 2 above, he seems to have grabbed something from her (pink clothing)