The influential Zen teacher and activist Roshi Tetsugen Bernie Glassman died Sunday morning in Massachusetts. He was 79.

The Zen Peacemakers, a global organization integrating Zen practice and social action that he launched in 1980, sent out a message to their members announcing his passing and saying that more details would be available at a later time. The organization, which he founded with his late wife, Roshi Sandra Jishu Holmes, had been called the Zen Community of New York until 1996. The Zen Peacemakers is perhaps best known for leading “Bearing Witness” meditation retreats, which take practitioners to the sites of terrible tragedies such as Auschwitz-Birkenau.

Glassman, who was born in Brooklyn, started studying Zen in 1967 with Taizan Maezumi Roshi (1931–95), who named him as his successor upon his death. Glassman went on to transmit the dharma to a number of well-known teachers, including but not limited to Roshi Joan Halifax, Pat Enkyo O’Hara Roshi, and Peter Muryo Roshi Matthiessen.

Glassman was also a prolific author, writing books such as Instructions to the Cook: A Zen Master’s Lessons in Living a Life That Matters, Infinite Circle: Teachings in Zen, Bearing Witness: A Zen Master’s Lessons in Making Peace, as well as The Dude and the Zen Master with Jeff Bridges and On Zen Practice and The Hazy Moon of Enlightenment with Maezumi Roshi.

In January 2016, Glassman suffered a stroke, from which he had partially recovered. He later discussed his rehabilitation and shared his thoughts on life’s great unknowns.

Glassman was also known as a social worker, an engineer, and a clown. In 2009, at the age of 70, he started a new project called the Zen Houses, which created residential dharma centers in impoverished neighborhoods, where Zen practitioners could also offer social services.

Tricycle is honored to have been able to call Glassman a friend for many years and to have had the opportunity to share his wisdom.

Related: Working in the Cracks

Related: Part 1 and Part 2 of an Interview with Bernie Glassman and Jeff Bridges