Thinking 'outside the box', maybe it wasn't HIS backpack/bomb. Maybe he saw one of the backpacks, picked up, and BOOM. Wrong place at the wrong time and curious.
Ref: Two Middle Eastern looking dudes seen running away from the scene.
/Whoa, had to adjust my tinfoil hat after that thought.
Very interesting take on things. That should be sorted out when they look back to see where he supposedly assembled he bomb. If they can't attach him to a bombmaking workshop then you might have something.
It's possible, maybe he was a victom, but at least we know it wasn't an Islmofascist suicide bombing like we had expected http://www.freerepublic.com/focus/f-news/1495393/posts