Define "natural". Sure as hell looks natural to me when I see a vulture eating a dead raccoon on the highway. Nature IS violent. Animals are violent. This world, like it or not, is a violent place. My parents had two sheep a couple years back. One of them killed the other from butting heads too many times. When two dogs meet for the first time, they size each other up to see who's Boss. If neither one will give way, they fight. If left uninterrupted, they may fight to the death. That, my friend, is nature.
Also animals are neither innocent nor guilty - I have never killed an innocent animal. Nor have I ever killed a guilty one. I have simply killed animals. If an animal kills a human, it is not guilty. Nor is it innocent. It simply IS. If you wish to lower yourself to the level of animals, you are saying there is no right or wrong, there is only "might makes right". Which is exactly how animals behave. By which you have made yourself, in effect, your own god, since you may decide what is right or wrong for yourself.
On the other hand if you try to raise animals to the level of humans, what about all those ants you step on or the flies you swat? By that reasoning you're a murderer every day, countless times over. So, you may be the first one to stop moving to avoid injuring any more ants.
I'm guessing by your commentary that you're an evolutionist. If so, remember this: if you ever chance to encounter a grizzly bear in a hungry mood, you're first on the menu. Point being, an animal has no sense of right or wrong. It doesn't care that you didn't do anything to it, all it knows is that it is hungry, and you look like lunch. Darwin's own hypothesis of evolution propounds "survival of the fittest". Animals kill to survive. The weak die, the strong live and feed on the weak. They won't stop, even if we do.
Now I believe I'll have a steak. And the next time a mosquito bites you, don't slap it. It's just trying to live - I suggest you teach it to drink nectar from flowers instead.