DRG VECTORS FOR A ILS RWY 23 APCH, THE PLT ALLOWED THE ACFT TO GET 400' BELOW THE ASSIGNED ALT OF 3700'. THE CONTROLLER (CTLR) QUERIED THE PLT ABOUT HIS ALT & THE PLT REPLIED HE HAD GOTTEN A LITTLE LOW, BUT WAS RETURNING TO THE ASSIGNED ALT. AFTER INTERCEPTING THE LOCALIZER (LOC), THE PLT WAS CLRD FOR THE APCH & TOLD TO CONTACT THE TWR. AS THE ACFT WAS ON FINAL APCH, THE TWR CTLR NOTED THAT IT WAS RGT OF COURSE & ADVISED THE PLT. THE PLT ACKNOWLEDGE, BUT MOMENTS LATER, THE ELT ACTIVATED AS THE ACFT HIT TREES ON THE CROWN OF A HILL & CRASHED. INITIAL IMPACT WAS IN LVL FLT AT AN ALT OF ABOUT 1700' MSL. THE ARPT ELEV WAS 1519'. THE DECISION HEIGHT (DH) FOR THE APCH WAS 1718'. DRG THE INV, NO PREIMPACT MALFUNCTION WAS FND, CONCERNING THE ACFT OR NAV EQUIPMENT, THAT WOULD HAVE RESULTED IN THE ACDNT. ABOUT 1 MIN BFR THE ACDNT, ANOTHER PLT, WHO HAD JUST COMPLETED THE APCH, RPRTD THAT HE HAD BROKEN OUT OF THE CLOUDS AT WX MINS.