There are numerous verses in the Bible that speak of killing beyond the command to kill animals. Animals are to be sacrificed under the Mosaic Covenant as part of their covenant with the Lord God.
There are various commands in the Mosaic covenant that outright demand killing those who violate the laws of God. In contradistinction of this, the Ten Commandments prohibit murder.
So what is the difference between killing and murder?
When someone is killed, this is done for a different purpose than what is suggested when someone is murdered.
A person murders someone because of unjust reasons. A person kills someone because of just reasons.
How can this be?
A person murders his wife and he is then killed because he has committed murder. Or a wife murders her husband and she is then killed because she has committed murder.
Murder is is unjust killing. Killing humans is a just and righteous killing executed because a societal law has been violated that has the penalty of death.
Under the Mosaic law, killing people who violated God's righteousness was sanctioned so the people could live their lives within a theocracy in accordance to the Omniscient Mind. Once a person has violated a law that demands death and the person is killed, that person is not tempted to do it again.
Effectively, killing is equivalent to cutting out the social cancers that would eventually destroy society. In the world today, we see much corruption and erosion of justice because people who are not really interested in loving their neighbor know they have nothing to fear as long as they can pay the lawyers (who later become judges). Or because they know that being under a certain age they are not considered legally culpable. This is especially happening in the West within the secular system that rejects morality and believes anything goes and the color of the required money is right.
To quote a lawyer from Detroit whom I had just heard asked how he expected an unemployable felon to pay his fee: "I got the murderer off the hook. I do not care how he gets my fee. All I know is that He has to pay me. If he doesn't, then I will have to use a collection agency."
From a New Testament perspective, the Romans killed Jesus at the behest of the Jews, who were intent on murdering Him, and the Mosaic Covenant has been nailed to the Cross of Calvary. Therefore there is no longer any requirement of God to kill anybody. Instead the New Testament concurs with the Ten Commandments which prohibits murder. In fact, all murderers are condemned to Hell, unless, of course, they express acceptable contrition before they die.