1997 Chevy S-10 Front brake sysytem

I changed the front brakes and rotors. I went on the test drive and it seemed as if the brakes were locked. They peddle went to the floor, and the car would not roll in first gear. I had to give it some gas for it to actuall move. At that time it almost sounded like the caliper was locking the pad onto the rotor. At that point I removed the the caliper and inspected it didnt see anything wrong that I could tell. I tired to open the caliper and it was stuck, I could not clamp it in at all. So I guess I have two question. Why did it seem like it was locked, and why cant I open the caliper now?