93 G20 key stuck and wont turn off

My van started fine now the key is stuck in the on position and wont turn off. I have been pulling the power fuse and disconnecting battery to turn off and restarting. Any ideas on what is causing this

Hopefully someone who Knows what the mechanism looks like will answer. In the meantime, my guess: i believe there is an interlock between the shift lever or shift mechanism, and the ignition switch. Its to prevent you from getting the key out with the tranny in anything but park. I think it possible that mechanism has hung up, and wont let the key turn even far enough to shut the motor off. Another possibility is that the electrical part of the ignition switch has -shifted- enough that turning the key wont shut the electricals down.