Denver Mayor Mike Johnston’s mother has died.

Johnston posted on social media Saturday that his mother, Sally Johnston, had passed away on Friday, calling her death “heartbreaking.”

Johnston called his mother “a tireless force for goodness” and described her as “so selfless and joyful and optimistic you couldn’t help but see the world as hopeful every time you saw her.”

He recalled her past as a music teacher in Boston in the 1960s who later went on to own the Christiania Lodge at Vail with her husband, Paul. She also served on the board of directors for Third Way Center, an organization dedicated to helping teens with complex mental health issues.

Johnston wrote that his mother was an inspiration to him.

“She changed my world, and she convinced me with a ferocity I will never surrender that we can all change the world, because I watched her do it every day.”