THE PLT HAD RECENTLY PURCHASED THE TWIN-ENG JET ACFT & HAD PLANNED TO FLY IT IN A PYLON RACE AT AN ANNUAL FLY-IN. THE PYLON RACE WAS ABORTED DUE TO POOR VISIBILITY IN TWILIGHT HAZE. THE PLT THEN MADE 3 HIGH SPEED/LOW ALTITUDE FLY-OVERS ALONG RWY 13. DURING THE 3RD FLY-OVER, THE ACFT WAS OBSERVED TO ROLL TO INVERTED FLT. HOWEVER, WHILE FLYING INVERTED, IT BEGAN TO DESCEND. SUBSEQUENTLY, IT IMPACTED THE GND BESIDE RWY 13, WHILE ON A SE HDG. THE ACFT WAS EXTENSIVELY DAMAGED BY IMPACT & GND FIRE; THE WRECKAGE TRAIL EXTENDED ABOUT 400 FT. WITNESSES RPRTD THE ENGS WERE RUNNING THRU-OUT THE MNVR UNTIL IMPACT. ALSO, WITNESSES RPRTD THAT WHEN THE ACDNT OCCURRED, THERE WAS SOME LIGHT IN THE WEST, BUT THERE WAS DARKNESS TO THE EAST. THE PLT HAD ONLY ABOUT 2 HRS OF DUAL INSTRUCTION IN THIS ACFT, NONE OF WHICH WAS IN AEROBATICS. NO OTHER FLT TIME IN THIS ACFT WAS VERIFIED, THOUGH HE HAD 2 BACK SEAT FLTS IN A SIMILAR MAKE & MODEL OF ACFT.