Occam's Razor Vonderek.
What's more likely? The cops saw an innocent kid on new years eve and they both spontaneously had the idea that it would be fun to gun him down. And the be forced fill out paperwork for weeks after, undergo a very lengthly investigation, have nightmares about killing someone for the rest of their lives, have to go to therapy, and maybe even lose their jobs or go to jail?
Or that a college kid had a few too many drinks, pulled out his reenacting rifle, and started acting in an unsafe manner, and the because of alcohol and shock, froze and did not drop the weapon he was carrying when police order him to?
Conspiracy by the police to murder in front of witnesses, despite the years of consequence it would bring? Or a drunk college kid doing some stupid things and winding up in a bad situation with no good judgment or reaction time due to alcohol.
I don't know about anyone else, but I think I can pick the more likely one out of those scenarios. But then again, I don't happen to own any tin foil hats.