I'm not an ASE or anything, but, in the "older days", a pedal sticking would have been caused by a stuck cable, carb problem, etc.. easy fix...but the brake would have only slowed down the car and not overridden the gas. In so many of today's cars, throttle "by wire" is how it's done...and when a computer controls everything in the car (and computers do crash and go on the fritz) then these kinds of problems can arise. From what I understand, our Edges have a brake override. If the ECUs in the 'yotas were told to accelerate the car, then it did, apparently overriding any other command that was coming in.
It's what we get when we change things from manual to computer controlled.