Don’t turn yourself in? How can they prove it was you? Don’t mention anything to anyone. Just go back to where you are living at. Claim to have no knowledge of anything. Worst comes to worst you tell them they beat you up so you ran outta town back to where you were living at. It wasn’t your gun. I hope you weren’t bleeding though cause if they find your blood at the crime scene you’re screwed. And you better hope that store didn’t have a security camera.