My Road bike pedals locked up tonight. Why?
If you didn't notice any broken spokes, it could have also been that the bead of the tire popped off the rim and caught on the brakes, preventing the wheel from moving and then ultimately dragging on the ground causing a blowout and maybe warping the rim.  Once the tube popped, it would no longer be pushing the tire in to the brakes and allowing your wheel to spin freely again.