What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
(-23) ATC became aware of a potential traffic conflict between cgesr and UAL287 with limited time available to avoid the conflict. ATC attempted to resolve the situation with amended altitude instructions to UAL287. Immediately after corrective altitude instructions were understood and acknowledged by UAL287, TCAS alerts were experienced both aircraft. TCAS alerts advised action contrary to controller instructions and the pilots of both aircraft elected to follow TCAS advisories. A climb was advised (by TCAS) to cgesr and a descent was advised (by TCAS) to UAL287. Required separation was lost however collision was avoided. All actions taken by pilots seemed timely and in accordance with issued ATC instructions up to the point of TCAS alert(s). Earlier recognition, by ATC, of potential traffic conflict may have prevented this incident.
As the FAA filed it
(-23) ATC BECAME AWARE OF A POTENTIAL TRAFFIC CONFLICT BETWEEN CGESR AND UAL287 WITH LIMITED TIME AVAILABLE TO AVOID THE CONFLICT. ATC ATTEMPTED TO RESOLVE THE SITUATION WITH AMENDED ALTITUDE INSTRUCTIONS TO UAL287. IMMEDIATELY AFTER CORRECTIVE ALTITUDE INSTRUCTIONS WERE UNDERSTOOD AND ACKNOWLEDGED BY UAL287, TCAS ALERTS WERE EXPERIENCED BOTH AIRCRAFT. TCAS ALERTS ADVISED ACTION CONTRARY TO CONTROLLER INSTRUCTIONS AND THE PILOTS OF BOTH AIRCRAFT ELECTED TO FOLLOW TCAS ADVISORIES. A CLIMB WAS ADVISED (BY TCAS) TO CGESR AND A DESCENT WAS ADVISED (BY TCAS) TO UAL287. REQUIRED SEPARATION WAS LOST HOWEVER COLLISION WAS AVOIDED. ALL ACTIONS TAKEN BY PILOTS SEEMED TIMELY AND IN ACCORDANCE WITH ISSUED ATC INSTRUCTIONS UP TO THE POINT OF TCAS ALERT(S). EARLIER RECOGNITION, BY ATC, OF POTENTIAL TRAFFIC CONFLICT MAY HAVE PREVENTED THIS INCIDENT.