CARGO TWIN TAKES OFF DIRECTLY INTO DEPARTING TFC AT NON TWR ARPT.

Narrative

WHILE IN THE FBO AT IMT; I HEARD AN AEROSTAR OPERATED BY A COMPANY THAT PICKS UP FREIGHT ANNOUNCE A 12 MI FINAL FOR RWY 19. A CESSNA IN THE PATTERN RETURNED HIS CALL AND TOLD HIS POS IN THE PATTERN AND THAT HE WAS PRACTICING LNDGS. THE AEROSTAR SAID HE WAS RUNNING LATE AND COULD HE GO IN FIRST. THE CESSNA SAID SURE AND THAT HE WOULD WAIT AND CIRCLE AND BE #2 TO LAND AFTER THE AEROSTAR. THE AEROSTAR LANDED ON RWY 19; TAXIED IN NEAR THE FBO; QUICKLY PICKED UP HIS FREIGHT AND STARTED TAXING OFF THE RAMP TO THE TXWY. A CARGO CARAVAN ON THE TXWY HAD TO COME TO AN ABRUPT STOP AS THE AEROSTAR CUT IN FRONT OF HIM ON HIS WAY TAXIING DOWN TO RWY 1. THE WIND WAS LIGHT AND VARIABLE. WHILE THE AEROSTAR WAS MAKING THE SHORT TAXI TO RWY 1; THE CESSNA PRACTICING LNDGS ANNOUNCED ON UNICOM 122.8 THAT HE WAS TAXIING INTO POS FOR TKOF ON RWY 19 AND THEN ANNOUNCED HE WAS TAKING OFF RWY 19 AND STAYING IN THE PATTERN. WHILE THE CESSNA WAS JUST LIFTING OFF; THE AEROSTAR SAID ON UNICOM HE WAS DEPARTING ON RWY 1 AND STARTED ROLLING OFF THE TXWY WHILE ADDING FULL PWR. I RAN FOR THE FBO'S UNICOM RADIO TO WARN THE CESSNA THAT THE AEROSTAR WAS COMING RIGHT AT HIM. THE CESSNA PLT SAID HE ALREADY SAW THE AEROSTAR AND WAS VEERING OFF TO HIS R. THE AEROSTAR PLT DIDN'T REPLY; HE CLBED ABOUT 500-700 FT AND MADE A R TURN HEADING E. ALL RWYS AT IMT ARE L HAND. THIS WAS WITNESSED BY MYSELF; 2 FBO EMPLOYEES AND I THINK THE CARGO PLT.