Suppose that you and somebody else shoot somebody at the exact same time. Because they would have died anyways, your killing them hasn’t caused any harm, and so is morally OK by your theory. However, the other killer is also morally blameless under your theory, because if they hadn’t killed the other person, you would have.
Suppose that you and somebody else shoot somebody at the exact same time. Because they would have died anyways, your killing them hasn’t caused any harm, and so is morally OK by your theory. However, the other killer is also morally blameless under your theory, because if they hadn’t killed the other person, you would have.
I believe that this requires a modification.