Murder, is an entirely human concept, I feel embarrassed to point this out actually. Other animals do not paint their behaviors in human terms. "Murder" in nature is only imposed by human observers and does not, and would not, exist without human observers. Humans are conscious animals that are able to interact with their world in ways other animals simply cannot. One way is through the imposition of 'laws' upon the world they see.
Unlike the laws of thermodynamics or of logic, abstract laws such as murder and stealing would not exist if humans were to disappear today and never return. The laws that govern the nature of our universe are independent of any observer and require only the descriptions that an observer will give them to become 'discovered'. Before scientists 'discovered' the laws of thermodynamics and all the other amazing rules that govern matter, these processes had been happening for billions of years. However, before humans 'discovered' ethics and morals and the laws that govern them (note that these two definitions of 'laws' differ substantially) they did not exist independently in the world.
The laws that we talk about in the natural world (aside from the sociological world) are only human constructs that we employ to share knowledge about our world. But I noticed a flaw in reasoning in your post that may be leading to your misunderstandings.
Natural selection does not predict that the "strongest and most aggressive' will survive, and that the presence of good in the world makes evolution untenable. This is a common misconception spread by American creationists and also personally interpreted by those who have not read Darwin at all. What is actually meant by the prediction of natural selection in Charles Darwin's theory is that only the individuals and species groups that are best adapted to changing environments will advance to maturity and breed, therefore passing along those favorable characteristics to their offspring - evolution. The strongest and most aggressive are sometimes a favorable trait passed on to offspring; but so is camouflage, small size, agility, endurance, patience, cognition, problem-solving, cooperation, speed, dexterity, illusion, sight, hearing, taste, appetite, and myriad other traits.