Forensic techniques have been advanced enough to discover this type of tampering with a crime scene for many years.
I advise that you consider that such an approach puts you at severe legal risk.
Unfortunately, I now live in a country where firearms are illegal, so my post is purely academic.
God forbid if you do shoot someone. Just keep repeating that you were afraid for your life. that's it or whomever you were defending's life.
If you tamper with the scene you'll just make it look like you were hiding something. Even if you weren't. I live in TEXAS (thank God) and if you're in my house or pose a threat that I deem life threatening you will hopefully be shot three times in the chest. Then I'll call 911 and try to save their life. But if you do have a weapon, it's actually more responsibility on you to act rationally, train and know the law.
Cause once you pull that trigger, that bullet is never coming back.
I just wish that we had open carry nationwide. From my experience, I've never seen a robbery at the gun store or firing range. But that's just my anecdotal and limited experience.