Be a pity for Mr Hinrich if an undercover agent trailing the young student "terminated him with extreme prejudice" before he could get into a crowd and maybe lose his backpack. Also, might have been distressing for any friends who may have accompanied Hinrich causing them to leave the vicinity in search of consolation. But then Hinrich may have been under the influence of something that prevented him from being too aware of his evening jaunt so perhaps he didn't mind.
FWIW, according to my ticket:
"11. Due to safety considerations, umbrellas are prohibited within the stadium.
12. All bags, backpacks, large cases for binoculars or other items, fanny packs and large purses (larger than 10" by 10") are prohibited. Only such items required for medical or family needs will be permitted. All carried items and entrants are subject to search."
Because of this, my wife did not even bring her purse to the game. I don't recall seeing any backpacks, although I saw purses that appeared to be at 10X10 (which is not all that large, really.) I can't say for sure how strictly these published rules are enforced, but I would honestly be a little surprised if they let in a kid with a full backpack - I suspect they would be searching it for alcohol, not explosives, but I don't think he would have just been waved in.
Do you think he tried?
My first thought when I saw that. You beat me to the possibility.