Rocket scientists they ain't - if you're gonna do something like this, ya gotta have escape planned and PLENTY of cash beforehand ...
If the report of suspect #1 having explosives taped to his chest are true. These guys might have been on suicide runs similar to 911. And they may have had wired bombs on them during the Boston Marathon drop just in case anything went wrong. After surviving the Marathon, they decided to go out in a place of glory around MIT.
Not a chance in the world that their mission commander planned for them to survive.
You don't think two teenagers from Chechnya thought this up on their own, do you?
They are PFCs in an army that goes up to the O-8 level. They were probably supposed to die on the scene. They CERTAINLY were not supposed to escape alive.