How far in did the piston go? It should retract until it is about even with the housing. If not, then it may be rusted/seized. Suggest removing it and blowing the piston out to see what state it is in. You have already exerted more force that usually required if you broke a c clamp.
------ Follow up post added September 24th, 2016 05:37 PM ------
Sorry, just saw this was for a 2014. Does it have an electric handbrake? If so, then you have to go into the computer to rewind the parking brake.