Patrick Mertens, 64, was in dire need of a kidney transplant. The generous staff at Kimball Elementary School had already spearheaded fundraisers to help him pay for ongoing dialysis treatment.

Even with their aid, Mertens’ condition continued to deteriorate. His daughter, Kayla, posted a Facebook plea for potential donors to come forward. Someone did—and it was someone they knew, third-grade Kimball Elementary teacher Erin Durga.

Durga and Mertens were more than nodding acquaintances. In addition to working at the same school, Durga’s three children attended the daycare facility run by Mertens’ wife, Lynda.

The co-workers often chatted about their families with one another after school. Durga also got to know and like Lynda, with whom she bonded at the daycare center while picking up her kids.

Even so, it was a huge leap from swapping casual stories about your families to donating a kidney, but Durga knew it was something she was simply had to do.

She told the Washington Post — “I felt in my heart, from the very beginning, that this was my thing. Once I decided that, yes, I’m going to donate to Pat, I felt really good about it, and I was at peace with it throughout the entire thing.”

Both patients emerged from the operation with flying colors and were well enough recovered to return to their jobs when the school year began in August.