You know.... it makes sense that the bomber didn't make it into the stadium. He could have bought a ticket outside okay... but they check backpacks etc pretty tight when you try to enter the stadium. (they're really checking for bottled water etc so that they can make you buy a 3$ bottle of water... but they do look in every back etc)
That's true, you're not getting into a stadium with a backpack unchecked. Sounds like said bomber was waiting for the crowd to clear out of the stadium, and the "package" went off prematurely. You don't need two pipe bombs to commit suicide. I'm afraid most suicidal young people aren't that imaginative.