I have to think this was done by an American terrorist probably acting alone. The bombs seem pretty basic, but I'm not sure how you manage to plant them in trashcans unnoticed or how long beforehand they were placed there. I'll bet on it being a white guy that is pissed of at something.He must have been nearby to detonate them. I can see slipping away in the confusion and tossing whatever device set the bombs off. He must be on video but you don't know what you're looking for.
IMO if this was Al-qita ( sp) they would have done a more efficient job and built better bombs and more of them they don't seem like they care much about being caught as long as they kill enough.
Seems like all you needed here is a pressure cooker, some sort of shrapnel, Gunpowder ( ?) and an electronic device to set it off....or even a simple enough mechanical device. It doesn't seem like you need an engineering degree to build it. Look back at what Timothy Mcveigh was able to do in OKC pre 9/11 !
Placing these fairly big pressure cooker things is what seems improbable to pull off. If you did it days before some trashpicker would think he found scrap metal ? Do it on race day and I think you look bad hiking in with a big backpack/dufflebag and throwing it in a trashcan, there must be people around 24/7 before an event like this !
The perp should be caught. The pressure cookers probably came from a Walmart not too far from Boston. The Gov't will find out who did this, or pin it on some schmuck that bought 2 pressure cookers and maybe looks like an easy target. I'm sure they know what brand/ model the cookers are and I assume they are identical.