ACCORDING TO THE PLT, THE WIND SOCK INDICATED THERE WAS LITTLE WIND BEFORE HE LANDED. HE RPRTD THAT AFTER LANDING ON RWY 7, THE WIND SHIFTED & A GUST BLEW THE ACFT TO THE RIGHT. SUBSEQUENTLY, THE ACFT WENT OFF THE RIGHT SIDE OF THE RWY & NOSED OVER. WITNESSES RPRTD THE WIND WAS VARIABLE & GUSTY AT THE TIME OF THE ACDNT.