Car will not start and stuck on drive

Okay, so here's the scenario: I just finished putting fuel driving to the gym. I pull into the parking space and I ease on the brake to come to a stop. I move the gear shifter forward into P from drive and the stick had no resistance. Usually you can feel a little resistance of the stick shifting but this time it was smooth very awkward. The gears on the dash still showed the truck in drive and when I let go of the brake the car started to move forward. I immediately put the parking brake on and turn off the car. I am trying to turn the car back on and it's not cranking. I know it's not the battery all the electronic in the vehicle is working fine. The truck is still showing the the gear on D and now I am stuck because I have no idea what's going on.