I laghted really hard on this...
I knew something was going to happen by the title but I didn't see the shoot scene coming... and in my opinion it could just end there :P
Anyway, the "Thought Process" (to the guy that didn't get it) or just the story line is:
She is crazy.
She wants to eat a d***.
She kills a man.
She eats his d***.
She feels happy.
One more thing:
You can't be getting worse, this is a really fun animation, and the drawning is good, just like the music choise ;)