They where chasing an armed perp, when he entered Central Park. Kate call for backup, Ryan and Esposito keep running, while Kate was given every details to dispatch. Rick was right behind her, when they start running again. They get to Dalehead Arch and they saw the perp, Ryan and Espo where on the other side of the bridge, when he start running to Kate and Rick, that's when Kate lost everything.
Xxx
It's been 15 years since everything change. She made a deal with CIA to keep her daughter safe, while they try to get the guy behind all this.
It was a clear night when she was dragged to a dark ally and Conan try to kill her, only to get busted by CIA agents. They make it look like she was dead and Conan did it, capturing Conan and realeasing him few hours later with no recollection about the interrogation they did on him and her look like she was stab multiple time, with the police saying it was a random act of violence.
She heard that Kate and Rick found Bracken and made a deal with him to keep everyone she love alive. She is so proud of her daughter, also very sorry for this hall story that didn't seem to get over.
Over the years she try to find the man behind this story, few days before Conan try to kill her, an agent from CIA came to her and tell her about Conan and the fact that she'll have to live like a ghost for a wille until they catch the man who keep Bracken in a short leash.