ACR Z TCASII UNAUTH DSCNT FROM ASSIGNED ALT NON ADHERENCE TO ATC CLRNC HAD LTSS FROM ACR X. EVASIVE ACTION TAKEN.

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THE ACFT INVOLVED WERE: 1) X T/SF34/A DCA-BOS J121 NEBOUND. 2) Y T/B73F/R FLL-ISP J121 NEBOUND. 3) Z T/DH8/A ISP-BWI J121 SWBOUND. Z WAS HANDED OFF TO ZCW SECTOR 59. DUE TO THE EARLY AUTOMATED HDOF; THE FULL DATA BLOCK DROPPED OFF; AND I MONITORED THE FLT'S LIMITED DATA BLOCK. X AT FL190 AND Y DSNDING TO FL210 WERE ACCEPTED FROM W59. SHORTLY AFTER X AND Y CHKED ON MY FREQ; I ISSUED TFC ON THE Z TO BOTH ACFT. Y WAS LEVEL AT FL210 OR JUST LEVELING OFF JUST PRIOR TO THE INCIDENT. Y ADVISED ME THAT HE HAD AN RA. I ASKED IF HE WAS CLBING OR DSNDING. ON THE SECOND REQUEST Y SAID HE WAS CLBING. AS Y WAS RESPONDING; I NOTICED THE LIMITED DATA ON Z START DSNDING. I REMEMBER SEEING FL196 IN THE LIMITED DATA BLOCK. AT THE TIME OF Z'S DSCNT; HE WAS ABOUT 3 MI HEAD- ON WITH X AT FL190. I TURNED X TO THE E TO AVOID WHAT I PERCEIVED WAS A POSSIBLE MIDAIR COLLISION. Y RPTED BACK AT FL210. I DO NOT RECALL SEEING ANYTHING OTHER THAN '210C' IN HIS DATA BLOCK. WHEN X WAS CLR OF Z; I TURNED HIM BACK TO COURSE. MY HDOF MAN CALLED W59 AS I WAS TURNING X. HE TOLD ME THEY SAID Z HAD A TCASII RA. SEVERAL MINS LATER; I ASKED X IF HE HAD AN RA. HE SAID THEY HAD A TA BUT NOT AN RA. HE ALSO SAID THAT THEY SAW THE TARGET COMING AT THEM ON TCASII AND WERE ALREADY TURNING WHEN I ISSUED THE TURN.