2000 Cavalier; Engine won't crank over

I have a 2001 Chevy Cavalier automatic transmission. The car never had any problems and drove great. Until one day I went to the store and as I went to park the car and put it park it would go in par. So I had to hold on the brake pedal. I freaked out and turn the car off. When I came out to start it up it didn’t do anything. However all my lights and everything still strums on. I soon to realize as well that the shifter was loose. What is the solution to the prom?! Please help