NEW YORK (CBSNewYork) — In an amazing story of friendship, selflessness and second chances at life, a mother’s best friend came to the rescue of a baby near death by volunteering to be a liver donor.

As CBS2’s Dr. Max Gomez reported, it is hard to believe that the chubby-cheeked little cherub named Finn O’Sullivan was ever near death. But just a few months earlier, he was born with not one, but two liver diseases that were destroying the vital organ.

“We have no good supportive care that can replace the function of the liver, so transplantation at this point is really the only option,” said Dr. Adam Griesemer of NewYork-Presbyterian/Columbia University Medical Center, “and given the two diseases that he had and the course he was taking at the time, he had only a few months to get this done.”

But neither Finn’s mom nor his dad was a match. That was where his mom’s childhood friend, Sarah McKitterick, did something to save Finn’s life.

“I actually had zero hesitation to be a liver donor,” McKitterick said. “As soon as I got the blood test and knew that I was a match, I was all in.”

After lots of testing to make sure she was healthy enough, McKitterick had about 15 percent of her liver removed and transplanted into baby Finn.

Even though the new liver improved Finn’s color and other vitals, it was a bumpy recovery – though McKitterick was out of the hospital in five days.

CBS2 was there for the emotional reunion when McKitterick saw Finn for the first time since leaving the hospital.

“I have no words,” McKitterick said. “I just feel honored that I got to do this. He’s such a good boy.”

When Gomez asked Finn’s mother, Kate Mullen, how to say thank you for such a gift, Mullen said, “I hope that Finn can just go on to do amazing things, and I think that that will hopefully make Sarah proud of the person that we will become.”

Five months later, Finn is a happy and healthy 1-year-old.

“Knowing that we can be planning a birthday party instead of the alternative is pretty amazing,” Mulelen said.

Finn will be taking anti-rejection drugs, probably for life. But his new liver will grow with him to match his larger body.

Within six weeks or so, McKitterick’s liver regenerated to replace the portion she donated. The liver is the only organ that can regenerate in such a fashion.