If the prosecution is smart, and by some unbelievable act of insanity the judge doesn't disallow use of the video in court, the prosecution should play that clip over and over and over.
Heaven knows the media certainly will. We have a murder
with/by an assault rifle
claiming castle doctrine!
as a defense.
It should be mentioned that the Brady Campaign is still somewhat effective in Minnesota, and this could be a beachhead for them to regain some relevance.