To understand my answer, take the following situation: An artist buys some expensive watercolor paper. He tells his young children not to cut it or draw/paint on it. Some days later, he himself take the paper, cut it up into the sizes he wants, and paint on it. Was he then “unfair” or “not practicing what he preach?”
No, he was not. The reasoning behind “do not draw on this paper or cut it” was not: “This paper has to remain in this condition forever.”
It was: “This paper is set aside for a purpose. I can use it for that purpose. My children cannot.”
Similarly, God made humans for a purpose. If we disobey God and kill, we kill people whom God could still have used. When God chooses to end a life, it is his perfect time. He made humans, he can take them into another realm when the time is right.
Superficially, preschoolers drawing a paintbrush over paper, and a skilled artist making a detailed painting, are both painting.
Superficially, God killing and humans killing are both doing the same thing.
But in both cases, only one of the two has a master plan.