NO KNOWN WITNESSES OBSERVED THE PLT PREFLT THE ACFT OR TAKEOFF. HE DEPARTED IN THE EVENING WHILE THE ARPT WAS NOT ATTENDED. AT APRX 2012 CDT, HIS SON OBSERVED & RECOGNIZED THE ACFT. AT THAT TIME, THE SON WAS AT HIS OWN HOME ABOUT 1/2 MI FROM THE PLT'S HOME. THE SON SAW THE ACFT OVERFLY HIS FATHER'S HOME AT LOW ALT. SUBSEQUENTLY, HE SAW THE ACFT GO OVER A TREE COVERED RIDGE BETWEEN THE PLT'S HOUSE & THE ACDNT SITE. THE SON STATED THAT THE ACFT STRUCK TREES ON THE BACKSIDE OF THE RIDGE & DISAPPEARED FROM HIS VIEW. AFTER HITTING THE TREES, THE ACFT IMPACTED IN AN OPEN FIELD & CAME TO REST ABOUT 185 FT FROM THE INITIAL IMPACT WITH THE TREES. EVENTUALLY, THE ACFT BEGAN BURNING. CLEANLY CUT TREE LIMBS (PROP CUTS) WERE FND WHERE THE ACFT STRUCK THE TREES. NO PREIMPACT PART FAILURE OR MALFUNCTION WAS FND. A CHECK OF THE PLT'S BLOOD SHOWED AN ALCOHOL LEVEL OF 0.239%.