The sunroof was open in tilt position and it shattered while i was driving down the highway at a speed of approx. 50 mph. it made a very loud sound. loud, like a gun shot sound. fortunately, it didn't make me swerve off the road or into the oncoming lane (if there had been an oncoming vehicle at the time, could have caused a collision) it was very startling. i was showered with splintered glass. there were no other vehicles nearby at the time it happened. there was no indication that the glass collided with anything to make it break. there was no obvious reason for the glass to shatter. the concern is that there may have been a defect in the glass. conditions:the temperature that day was in the high 80's to 90 degrees. i also had the rear window opened at the time of the incident.