I had that happen to me once when I had my 1983 GMC Jimmy. I closed the door and the glass just up and shattered into a million little pieces.
It could be that a hairline fracture was at the base of the glass and one good thunk was all it needed to break completely..
'92 300CE - Sold
2004 C240 - C7 Wheels
2015 ML350 - P1, Pano, Ash poplar wood, Sport Dinamica interior, Running Boards Keyless go.