from what we know the kid saw the guy walking to the school buulding and also saw him put the sidearm back in the car and then walk back to the school building.
thus if the snitch had used reason/logic/actually was thinking s/he could have seen there was no incident here. but the kid is a product of big brother and did exaclty as a mindless drone would.
That's the way it seemed to me as well.... and I drew the same conclusion.
My kids, while in high school, would have acted differently. Then when they went away to college it all changed and they might have done what happened here. The difference is if they had talked to a parent they would have been reminded that nothing happened, and the carrier put the firearm back in his vehicle so it was an honest mistake.