thats crazy bro,,, i work on a shop and does brakes but never encountered this kind of situation..

anyways, with your description, i know for a fact that the brakes were on all the time from wherever you left off. the only thing that will activate the brakes is between the brake pedal and your master cylinder.

master cylinder is good because if its bad it does the opposite (you loose brake pedal pressure) .

your friend might have done something with the brake pedal or have fogotten to put back a spring or something.

or maybe you just dont have anymore brake pads @ the rear brakes and fronts causing a metal to metal contact.

not good. new parts will be required sorry