I have trouble believing that his handlers would detonate him at the bench. If they were watching him the whole time, they saw all of his unsuccessful attempts to get into the stadium. Why would they allow him to go to the bench and blow him up there, away from the stadium, and cause no casualties other than Hinrichs himself? It makes more sense for them to have detonated him while he was still at the stadium. Realizing that he was having trouble getting in, and running out of patience, they would blow him up there in hopes of at least creating panic inside the stadium. Blowing him up at the bench accomplished nothing.
If someone did detonate him at the bench, it makes more sense for it to have been our people who did it.
They may have thought he was going to ditch the backpack and squeal on them