WITNESSES RPRTED THE ENG DID NOT SOUND LIKE IT WAS PROVIDING FULL POWER DRG TAKEOFF & THAT ABT 3/4 OF THE 3600' RWY WAS USED FOR THE TAKEOFF ROLL. AFTER LIFT-OFF, THE ACFT CLIMBED AT A SHALLOW ANGLE TO ABT 250 TO 300 FT AGL. IT THEN ENTEREDA SHALLOW LEFT BANK. AFTER TURNING ABT 90 DEG, ITS NOSE PITCHED UP & THE ACFT CLIMBED ABT 100 FT. THE ACFT THEN SNAP- ROLLED TO THE LEFT, ENTERED A DSCNT & CRASHED NEXT TO A STORAGE BLDG IN A RESIDENTIAL AREA. AN INVESTIGATION REVEALED THE ACFT WAS LOADED TO NEAR ITS MAX GROSS WT LIMIT. NO PREIMPACT PART FAILURE OR MALFUNCTION WAS FND. THE ENGINE WAS SATISFACTORILY TEST-RUN AT RATED POWER. THE LNDG GEAR WAS FND IN THE FULLY RETRACTED PSN & THE FLAPS WERE FND FULLY EXTENDED. USING THE OWNER'S MANUAL, THE TAKEOFF DISTANCE WITH 15 DEG OF FLAPS (TAKEOFF FLAPS) WAS CALCULATED TO BE 977'.