200 rounds of rifle ammo is pretty harmless when coupled only with a loaded .45 semi-auto pistol. Most .45 semi-auto pistols have a max magazine capacity of 8 to 10 rounds. If this guy "intended to shoot up a high school football game" then it looks like he was a very poor planner.
“... he was a very poor planner”.
Especially since the football game had been played a few hours later. Not sure about other schools but our high school essentially tells the kids to go home after a game. Everything is wrapped up (equipment put away, players going home etc) within an hour after the game. I’m not saying this guy wasn’t a nut job but I don’t see the intent to shoot up a game. IMHO.