What I’ve not heard is - why did they kill the MIT security guard? The commissioner said it was an “assassination”, but weren’t they trying to get away? And just happened to show up at a c-store while it was being robbed? Odd coincidence, to say the least.
I think you stumbled on the weakest link in the "official" story. If you put together the killing of the MIT security guard and announcing they were the Boston Marathon bombers to the "car-jacking victim", you can only guess that they wanted to be caught, or at least wanted a confrontation.
Or, were they a diversion???