Black Market

You throw the ball at the target and hit it directly in the center. It swings back and the seat under the mouse drops. The mouse screams.

"WHY????"

The mouse splashes into the water and starts screaming in utter agony. You look through the glass of the tank and see the mouse's skin and flesh dissolving. The wiry rat begins to cackle maniacally. It appears the tank was full of acid. 

Eventually, the skeleton of the mouse sinks to the bottom of the tank, streaming bubbles as the acid works its way through the more sturdy bones. It's probably a good idea to leave the scene of the crime.