DURING ARRIVAL, THE PLT WAS ADVISED THAT THE ARPT WX HAD JUST CHANGED TO IFR. HE WAS ASSIGNED AN ALT (2900 FT MSL) & PROVIDED A VECTOR FOR AN ILS APCH. SHORTLY THEREAFTER, THE PLT ADVISED THAT HE WAS 'HAVING MOTOR DIFFICULTY & NEEDED TO COME STRAIGHT-IN.' HE WAS PROVIDED A VECTOR TO THE ARPT, BUT THE ACFT WAS LOSING ALT FAST. SUBSEQUENTLY, THE PLT LANDED GEAR UP, ON A BOULEVARD, WESTBOUND. DURING THE LANDING, THE ACFT STRUCK A STEEL STREET SIGN, A WESTBOUND AUTO, 2 STEEL STREET SIGN POSTS & A CONCRETE GUARDRAIL, THEN BURNED. TWO PASSENGERS ESCAPED BY KICKING OUT A LEFT REAR WINDOW & CLIMBING OUT. THE 3RD PASSENGER WAS UNABLE TO EXIT THRU THE WINDOW, WAS SERIOUSLY BURNED & SUBSEQUENTLY DIED. THERE WAS EXCESSIVE FIRE DAMAGE TO THE RIGHT WING. DAMAGE TO THE LEFT WING WAS MINIMAL EVEN THOUGHT THE LEFT FUEL TANK WAS RUPTURED. ONLY A FEW DROPS OF FUEL WERE OBTAINED FROM THE LEFT TANK. FUEL CALCULATIONS REVEALED THAT THE ACFT SHOULD HAVE CONSUMED ABOUT 44.5 GAL SINCE IT WAS REFUEL. USABLE FUEL IN EACH TANK WAS 44.5 GAL.