Closer analogy would be you accidentally kicked a hammer hidden in the tall grass (no foreknowledge), and it flies up and hits the cat. Now it gets murky? Are you at fault for not being perceptive enough? Is the owner of the hammer at fault for not keeping track of it (since he/she may not have made the move that hid it in the grass)? Is the manufacturer at fault for not making the hammer easier to see? There's enough wiggle room that any of those three liabilities can apply.