AN ACR B757 INBOUND TO SXM ON VISUAL APCH GOT A TCASII RA ON AN ACR ATR72 BELOW HIM. THE B757 TOOK EVASIVE ACTION TO MISS THE ATR72 AND ADVISED THE TWR OF THE NEAR MISS.

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DSNDING INTO SXM ON VISUAL APCH 25 NM OUT. NO TA. POP UP TCASII TARGET ABOUT 2 NM 700 FT BELOW US. WE WERE IN STEEP DSCNT. TOLD FO TO LEVEL IMMEDIATELY. AS HE WAS LEVELING WE RECEIVED AN RA TO CLB IMMEDIATELY. RESPONSE WAS MADE AS TARGET WAS CLOSING RAPIDLY IN DISTANCE AND ALT. VISUAL CONTACT WAS ESTABLISHED AT ABOUT 1/2 MI WITH 200 FT SEPARATION. WE WERE STILL FOLLOWING RA AND CLBING AT 1500 FT PER SECOND. CLOSEST APCH TO OTHER ACFT WAS ABOUT 200 FT DIRECTLY UNDER US. OTHER ACFT WAS AN ACR ATR. SXM TWR ADVISED THAT WE HAD LEVELED OFF TO AVOID TFC. WITHOUT TCASII THIS COULD HAVE BEEN MUCH WORSE. THE TFC IN AND OUT OF SXM IS BECOMING VERY HVY. ONE PERSON IS HANDLING GND CTL; TWR; APCH; AND DEP! IT IS GETTING OUT OF HAND; DESPITE A HEROIC EFFORT BY SXM CTLRS. IN ADDITION TO THE EXCESSIVE TFC ON THE ONE FREQ; ANOTHER NEARBY TWR USES THE SAME FREQ! TO FURTHER COMPLICATE THE ARR; IT IS ALMOST ALWAYS A SLAM DUNK DSCNT. A HEADS UP TO EVERYONE FLYING INTO SXM TO BE EXTREMELY VIGILANT IS IN ORDER; ESPECIALLY IF THE CLOUD COVER IS MORE THAN SCATTERED.