NMAC. WHEN ON A NIGHT APCH AT TWR CTLED ARPT; RPTR PLT SAW A GREEN LIGHT PASS IN FRONT OF HIM AND QUERIED TWR ABOUT OTHER TFC. TWR GAVE RPTR AN IMMEDIATE TURN AND TOLD RPTR THAT THE OTHER ACFT WAS NOT IN RADIO CONTACT. THE OTHER ACFT; AN AG TYPE; LANDED AND TAXIED AROUND ON THE ARPT BEFORE DEPARTING.

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WHILE ON FINAL APCH TO RWY 32; WITH LNDG CLRNC; 1/2 MI FROM THE NUMBERS; WITH MY LNDG LIGHT ON; RECOGNITION LIGHTS ON; STROBE LIGHTS ON; GEAR DOWN; FLAPS DOWN; 80 MPH; GND TERRAIN NOT VISIBLE DUE TO DARKNESS; I CAUGHT A GLIMPSE OF A NBOUND GREEN LIGHT PASSING IN FRONT OF ME AND THEN PROP WASH. I THEN LOST SIGHT OF GREEN LIGHT. I CALLED THE TWR AND ASKED IF THERE WAS ANOTHER AIRPLANE IN THE PATTERN. TWR RESPONSE 'MAKE AN IMMEDIATE L TURN; HE'S LNDG IN FRONT OF YOU OR RWY 32.' THEN I ASKED THE TWR IF HE HAD HEARD HIM ON THE RADIO AND TWR REPLIED; 'I HAVE NOT BEEN TALKING TO HIM.' I THEN REPLIED MAYBE THERE IS AN EMER AND FLEW OVER THE ACFT THAT HAD LANDED AND STOPPED ON RWY 32. I OBSERVED AGRICULTURAL CATEGORY TURBINE BI-PLANE WITH ENG RUNNING; RED AND GREEN POS LIGHTS OPERATING; NO WHITE TAIL-LIGHT; AND OBSERVED THE ACFT TAXI ON TO RWY 23. I GOT CLRNC TO LAND ON RWY 32. AFTER LNDG I OBSERVED AGRICULTURAL ACFT TAXI IN CIRCLES MANY TIMES ON DIFFERENT AREAS ON THE RAMP AND HE THEN TAXIED IN BEHIND ME AND FOLLOWED ME TO MY HANGAR; TURNED 3 CIRCLES AND TAXIED BACK OUT OF SIGHT. I FEEL THE TWR PERSON WAS RESPONSIBLE FOR PREVENTING WHAT COULD HAVE BEEN A TRAGIC ACCIDENT.