Yeah ok, this is just odd. I don't see how you can make any sense in just up and shooting yourself for any reason, never mind it being because he had some turtle soup. But then I'm rather against the idea of suicide. And this is CK9 after all. But still, I think your riddle makes no sense!
Would he have shot himself over any other kind of soup?
... beverage?
... food?
Is this "turtle" soup really made with turtles?
Is there any other significant ingredient in the soup?