HELP - -95 Sable WON'T shut off!!

Okay, here's the strange but true events! We started the car and I noticed the radio, turn signals and clock were not working - first thought a fuse! The ABS light and the Emergency brake light were lit on the instrument panel also. Drove approx. 2 blocks. Went to put the car in park and passing Nuetral it made a horrible screaching sound, fine past Reverse and the same noise when it went into Park. 2nd thought Transmission... Now here's where it gets really odd. Went back up through the gears to Drive and it didn't make the noise , but it did when shiftting back down again... Tried to shut the car off -now the radio and clock were working again and the dummy lights on the instrument panel for the braking systems were off. Turned the key back to shut off the car and NOTHING it was still running. Popped the hood and disconnected the Positive Battery cable - no change - everything including the lights Still On. Disconnected the Negative Battery cable. Everything was still running - lights, radio, car everything!! We left it running for just over half an hour and no change - everything was still running. We finally got it shut down after pulling a fuse inside the engine compartment. We even tried the Fuel shut off in the trunk to no avail. ANY IDEAS?????? We are baffled here.:banghead:

If your vehicle is still running when your turned the ignition switch to off then more than likely your ignition key cylinder may need to be replaced or wires in the ignition key cylinder needs checking for short, etc. Your vehicle is still running when you disconnected the positive terminal on the battery because the alternator is still providing electrical power to the engine while the engine is running.