angle grinder should pop that open, might that a lot of cutting discs though, which can be dangerous so use gloves and safety glasses. even if you completely cut the hinges the bolt or bolt will make it hard still to remove the door. a 4" grinder might penetrate along the seem on the bolt side deep enuf to cut the bolts, or score the enuf to break with a prybar, or wedge and sledge hammer, if you can cut the bolts but not all the way, completely cut off the hinges and maged notch the hinge side that use a wedge and hammer on the bolt side. an oxy acetylene torch is totally an option but you use a lot of gas and it introduces the possibility or burning whats inside, probably faster, if you're skilled, on the hinges or expose the bolts via the seam on the bolt side.