I'm curious about your comment on the timing of the blast, right before halftime, why are you suspicious?
Because a lot of people leave the stadium to go get a beer and are given passes to get back in. My son's fraternity brother left a few minutes before the blast to go back to his house to change and was going to come back. If this bomber had gone in the crowd during halftime, about half or more the stadium is down below getting food, going out for drinks, and smoking. The area under the parking garage across from Cross is very large and packed with concession stands.
If he got in there, it would have caused a lot of panic and injuries IMHO.