Is "proof" that it was not an AR15. Being familiar with firearms I was confused when I saw the video supposedly showing a cop removing the "rifle" from the trunk. When I saw the officer rack the action several times it was clear to me that this was no AR15. I was aware that supposedly a shotgun had been involved and the only shotgun that I could think of that would match what I saw was a Saiga shotgun. Later on when the incompetent media corrected themselves I learned that this was indeed a Saiga.
Putting on my tinfoil hat, I put "proof" in quotes above because I have no evidence that the video I saw was of events at sandy hook other than the nice commentator telling me so.