Alpha, Beta and Gamma are in a desert. Alpha don’t like Gamma and hence decides to murder him. He poisons the water supply of Gamma. Since it is the desert area, Gamma must drink or he will die of thirst.
Beta does not know of the actions of Alpha and also decides to murder Gamma. To succeed in his ill motives, he removes the water supply of Gamma so he dies of thirst.
Gamma dies due to thirst. Who murdered Gamma?
The answer to this question might sound more of a philosophical one.
It is Beta whose action led to Gamma's death directly. It was the scarcity of water that led to his death ultimately. It may be the circumstances prevailing his demise and not a specific person who killed him.