PLT ORIGINALLY PLANNED APCH TO RWY 17 BUT CHANGED RWY WHEN INFORMED BY ANOTHER ACFT THAT RWY 35 WAS THE ACTIVE. TWO WITNESSES REPORTED WINDS AT THE TIME WERE FROM THE EAST, ONE STATING 5 TO 7 MPH THE OTHER STATING LIGHT AND VARIABLE. PLT STATED APCH SPEED OF 95 KTS WAS FLOWN BUT GROUND SPEED SEEMED FAST. A WITNESS STATED N7846Q TOUCHED DOWN OVER 1/2 WAY DOWN THE RWY. PLT STATED, AFTER TOUCHDOWN A TAILWIND WAS INDICATED BY THE WIND SOCK AND REALIZING THERE WAS NOT ENOUGH RWY LEFT TO GO-AROUND, BRAKES WERE APPLIED. THE ACFT ROLLED OFF THE END OF THE RWY AND INTO A CULVERT. SKID MARKS WERE FOUND ON THE RWY STARTING NEAR THE WITNESSES ESTIMATED TOUCHDOWN POINT AND CONTINUING OFF THE END OFF THE RWY. ONE WITNESS WHO REPORTED WINDS FROM THE EAST STATED THAT 45 MINUTES LATER UPON RETURNING TO THE ARPT, THE WINDS HAD PICKED UP AND WERE NOW FROM THE SOUTH.