Cracked driver side window

[flouese]

Took the car out for a nice top down ride last night. After the top went up and I rolled the windows up, I heard a "grinding" sound from the drivers side. Rolled the window down and then back up, no sound. Investigate in the morning. Went out in the morning, and discovered a 6" crack heading from the top center, curving down towards the front of the car. Crack can only be felt from the inside (for now). Any thoughts on cause?

Are there any "oh-by-the-way" tips (lessons learned) for removing door panels that isn't covered anywhere?

Thanks

Fred in Florida