CHICAGO -- Until Wednesday, Kimberly Cooper and Brendan Flaherty were strangers. But now, they share an unbreakable bond.

"Thank you very much for giving me the freedom to be able to live my life the way I want to live it, not tied up to a machine 10 hours a night," Brendan said.

Kimberly's kidney now lives in Brendan's body, one of six kidney transplants performed last week at Northwestern Memorial Hospital. Each one of them can be traced back to Kimberly's act of generosity.

"You're like, oh my God, really? Six people were saved just because I chose to be selfless for a day," Kimberly said.

Philip Cameli and Brendan Flaherty CBS News

This was not necessarily meant to happen, because -- well, it's complicated.

Brendan thought he'd get his friend Phillip Cameli's kidney. But that didn't match and he ended up with Kimberley's kidney. Philip went ahead and donated his kidney anyway and started a chain reaction.

"I've made a lot of selfish decisions in my life," Phillip said. "I thought that this would be a really great opportunity to kind of amend those decisions."

A group of patients who got the kidney donations they needed met Wed., February 28, 2018. CBS News

It turned out Philip's kidney was a match for Clotilde Ruiz, whose daughter Daisy was rejected as her donor. But Daisy's kidney worked fine for Scott Rial, and so it went until a dozen donors and recipients were matched. All of them met for the first time Wednesday afternoon.

"I'm going to have a lineage to someone who's going to live on," said Kimberly. "That's more than money and that's more than words."