Is killing someone "wrong" in a different way than just morally?

It is commonly accepted that one human killing another is immoral, and therefore, illegal. As far as I know, most countries have laws that punish convicted murderers with either jail time or execution.

Emotions aside, (I’m sure there are many Flutherers who have known a friend or a family member that were killed by someone, etc. and I don’t mean to belittle these potential victims…) is murder strictly immoral? It seems natural for members of the same species to compete for survival, and in some cases, this means killing peers/competition.

I assume that humans are more advanced than (generalization) the rest of earth’s animals, but we are still animals. Should there be certain factors that constitute an acceptable or unacceptable murder? Discuss.