After carefully wiping down his weapon and wrapping the dead perp's hands around it, he takes it back and puts it down on the countertop. When the police arrive, he tells them "I was fortunate enough to see him distracted and take his pistol from his hand. But he pulled out another one, so I had to shoot him in self defense, in fear for my life".
This may sound plausible, in a fiction novel sense, but in reality, forensic techniques have advanced so far that there is little chance of avoiding detection. If you were justified in shooting, the physical evidence will agree with your story. We must fight the unconstitutional laws in the legislature and the courts and in the court of public opinion. In the Nation, we are winning.