a big cloud of white smoke came out the exaust pipe , now it wont start on 2003 Buick Century

my car started to stall, then revved up and a thick cloud of white smoke came out my pipe, and it wont crank. wasnt running hot or driving funny before this..

Asked by for the 2003 Buick Century
Wont start or wont crank as in engine WON'T spin over? If so, do not try to start anymore, may damage engine if liquid locked from head gasket leak! Can pull spark plugs to see which cyl. affected but be carefull may still be under some pressure! Just have seen this whole scenario before on this GM engine, may not be applicable here!