95 intrepid trans locked up

95 intrepid 4 speed auto car was running fine this morning stopped at store came back out and the trans is locked up it acts like it is in gear but won't move and i can't push the car when it is running but it rolls fine when it is shut off seems like it is stuck in park any help please

I'm gonna save a 94 from going to the junkyard this weekend cuz the guy was driving through his neighborhood and the wheels locked up. He said it gave no warning, seemed like it went to park by itself. The shifter was in drive, he couldn't move the car no matter what gear it was in. After the car sat for a while it did move about 100 yards and he said the motor 'loaded up' and the car stopped again. He had the tranny rebuilt about 4 years ago and it cost him alot. Now he don't trust it and wants to send it to the junk yard for $250. The car is in great shape and the 3.3 engine runs fine. Not sure if it will move with the engine off. I'll be sure to try that when I'm putting it on the trailer. If it moves with the engine off, it's gotta be electrical. Don't know what damage was done when it locked up at 15 MPH though. One tranny shop said they could rebuild that tranny for $1000. Could be a good school car for $1,250. Hell it's better than what I drive now. I'll give the kid my 93 Escort and drive the Trepid. I just don't give up on cars that easy. Even if it is a MOPAR.