Dr. Paul Farmer, global health champion, Harvard Medical School professor, anthropologist and co-founder of the nonprofit health organization Partners in Health, has died at age 62.

According to the tweet, Farmer “unexpectedly passed away today in his sleep while in Rwanda,” where he had been teaching for the past few weeks at the university he co-founded. A source close to Farmer said he had been in Rwanda for the past several weeks teaching at the University of Global Health Equity, the medical school that he helped found with the country’s former minister of health, Dr. Agnes Binagwaho.