Pope Francis on Sept. 8 celebrated a former student of his who is now sometimes called Madagascar’s “living saint” for having changed the lives of thousands of poor people who once lived in garbage dumps.

Thousands of former slum dwellers, many of them children, gave the Pope an ecstatic welcome, leaving him seemingly overwhelmed by the experience, who only hours earlier defended the poor in the homily of a huge open-air Mass..

Francis taught Father Pedro Opeka theology at the Colegio Máximo de San Miguel in Buenos Aires in 1968 while Francis was completing his own studies for the priesthood.

Over the last 30 years, an organization founded by Opeka, whose parents emigrated to Argentina from Slovenia, has built homes for 25,000 people, 100 schools, six clinics and two football stadiums across the island nation. Next year, he plans to build a college for paramedics.

The white-bearded, jovial Opeka, 71, has been called a “living saint” along the lines of Mother Teresa of Calcutta by many in Madagascar because of his work in one of Africa’s poorest countries. He has been nominated for the Nobel Peace Prize.

The Pope met families living in Akamasoa, one of the first villages built by Opeka on the hills above Madagascar’s capital Antananarivo to re-house people living on the municipal dump in the valley below.