NMAC BTWN A B757 DSNDING THROUGH 8200 FT AND 2 ACFT -- ONE A LOW WING IN A STEEP BANK MANEUVERING 100 FT OFF THE L WING; AND ANOTHER ACFT THAT CAUSED A TCASII RESPONSE; BUT NOT SIGHTED.

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WE WERE DSNDING TO CROSS DYLIN AT 8000 FT ON THE DYLIN 1 ARR TO EWR. TA ALERTED TO AN ACFT 700 FT ABOVE US TO THE L. WE LOCATED IT; THEN GOT RA WITH INDICATION TO CLB. STARTED CLB TO ABOUT 8300-8400 FT. I STARTED BACK TO THE R AS CLB INDICATION MADE NO SENSE; BUT TCASII MAY HAVE ALERTED ON SOMETHING ELSE. WE ARE TRAINED TO FOLLOW THE COMMAND BARS ON TCASII RA. NEXT WE SAW A LOW WING SINGLE ENG ACFT VERY CLOSE ABOVE -- 100 FT -- MANEUVERING AND IT PASSED OFF OUR L WING GOING SW. AS I LOOK BACK ON THIS; THERE MAY HAVE BEEN 2 ACFT. ACTUALLY THERE HAD TO HAVE BEEN 2 ACFT FOR THE TCASII TO GIVE US THE COMMANDS IT DID. ON THE FIRST TA I SAW THE PLANE AND IT APPEARED TO BE BANKING AND MANEUVERING STEEPLY. PERHAPS WE FLEW THROUGH 2 PLANES IN A DOG FIGHT. THE ONE I SAW WAS A SINGLE ENG LOW WING ACFT. IT WAS CERTAINLY SCARY. WE RPTED TO APCH THAT WE HAD TAKEN EVASIVE ACTION. I TALKED WITH THE CTLR'S SUPVR LATER. I DON'T THINK OUR CTLR REALIZED WE'D HAD AN NMAC; AS HE DIDN'T KNOW WHY WE WANTED HIS PHONE NUMBER. BY THE TIME HE LOOKED AT US ON THE SCOPE WE HAD CORRECTED BACK AND HIS CALL OF 'YOUR AT 8100 FT' DIDN'T MAKE SENSE TO US. THIS WAS A BEAUTIFUL CLR VFR DAY WTH CALM WINDS AND MY TCASII ALERTED TO NO LESS THAN 3 TA'S AFTER OUR RA HAPPENED IN THE 15 MINS IT TOOK US TO FLY TO EWR -- LNDG N. THESE TA'S WOULD HAVE BEEN LEGAL VFR FLTS. THE SUPVR SAID 'YEAH; THE LA GUARDIA PLTS USED TO COMPLAIN ALL THE TIME ABOUT THIS. IT'S A VERY DENSELY POPULATED ARPT AREA.'