Box Turtle squirts yellow slime

I was trying to save a box turtle from possiby getting hit by a car.I stopped to pick it up to release it in the woods.When I picked it up it was very wiggley trying to get away. When I got in the car it squirted a lite yellowish slimey stuff from it's backside.It was all over the seat,console and carpet.I has to wrap a towel around it until I got home to the wooded area.There was no smell(thank heaven)I put it on the grass while I cleaned my car. It did not move. When I picked it up to put in the woods, it clamped up tight in it's shell.I have handled turtles all my life and I have never had this happen.Does anyone know what it was and why it did this?