THE RPTR EXPERIENCED VISUALLY SEEING THE LIGHTS OF AN ACFT; THEN RECEIVED A TCASII TA; THEN A CTLR INSTRUCTION TO TURN; AND THEN A TCASII RA TO FIRST DSND AND WHILE THE RPTR WAS PONDERING THE TCASII RA COMMANDED A CLB FROM 4000 FT TO 4250 FT AS THE TFC PASSED UNDERNEATH.

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DURING RADAR VECTORS FROM BWI APCH AT 4000 FT TO THE ARPT; WE WERE GIVEN A HEADING OF 240 DEGS. APPROX 2 MINS AFTER FLYING THIS HEADING WE SAW LIGHTS FROM ANOTHER ACFT. DURING THE TIME WE WERE DISCUSSING THE ACFT AND ITS RELATIVE POS AND MOVEMENT TO OUR ACFT; THE TCASII ISSUED A TA. THE TCASII INDICATED THE ACFT WAS 200 FT BELOW OUR CURRENT ALT OF 4000 FT AS THE TCASII WAS ISSUING THIS ADVISORY. BWI APCH CTL BEGAN TO ISSUE A TFC CALL. THIS CAUSED A BIT OF CONFUSION BTWN US (THE CREW MEMBERS) BECAUSE OF OUR OWN DISCUSSION; THE TCASII AND ATC. AT THIS TIME; BWI ISSUED AN ADVISORY TO TURN R TO AVOID THE TFC AT NEARLY THE SAME TIME TCASII ISSUED A RA TO DSND. THIS ADVISORY CAUSED EVEN MORE CONFUSION BECAUSE WE COULD SEE THE ACFT ALT INDICATED 200 FT BELOW OUR OWN ALT. ALMOST INSTANTLY THE TCASII THEN ISSUED A CLBING RA. WE STARTED A CLB AND REACHED AN ALT OF 4250 FT AS THE TFC PASSED SLIGHTLY L AND BELOW OUR ACFT. OVERALL; THE TCASII DID AN EXCELLENT JOB OF RAISING AWARENESS OF THE TFC AND SUGGESTING THE BEST EVASIVE ACTION. MY BIGGEST CONCERN IS THE TREMENDOUS AMOUNT OF INFO THAT OCCURRED IN THE LESS THAN 1 MIN THE SEQUENCE TOOK PLACE. BTWN OUR OWN DISCUSSION; ATC ISSUING TA'S AND THE TCASII; IT COULD EASILY HAVE CAUSED A DELAY IN REACTION TIME. THIS BEING BECAUSE OF THE TIME NECESSARY TO PROCESS ALL OF THE INCOMING INFO. THIS DELAY COULD HAVE BEEN CRITICAL IF THE CLOSURE RATES WOULD HAVE BEEN HIGHER.