David Shapell, a Jewish immigrant from Poland who became a successful California real estate developer and gave millions of dollars to organizations focused on Holocaust remembrance, has died. He was 94.

Shapell was hospitalized in Tel Aviv while he and his wife, Fela, were visiting Israel to celebrate the birth of a great-grandchild. Suffering from lung cancer and pneumonia, he died Feb. 8, his daughter Rochelle Shapell said.

Shapell, his brother Nathan and his brother-in-law Max Webb started Shapell Industries, a firm that over five decades built some 70,000 homes throughout California. The company was sold in 2014 for about $1.6 billion.

In 1979, Shapell’s three children persuaded him and his wife to revisit the Polish hometowns that held painful memories for them. Fela, who was imprisoned in the Bergen-Belsen concentration camp, was from the town of Auschwitz. Shapell was from Wolbrom, where the Nazis removed several thousand Jews and shot the remaining 300 men after marching them to a mass grave. His father was probably among them. At the site of the mass killing, David Shapell saw signs of recent digging — apparently the work of treasure hunters who believed that Jewish murder victims might have carried gold and jewels to their deaths.

“What he did afterward was so symbolic of his personality,” Shapell’s son Irvin said. “He somehow found a way to get the gravesite cemented over so there could be no further digging.”

In 2014, David and Fela Shapell gave $15 million to the U.S. Holocaust Memorial Museum to help with the construction of a massive repository for Holocaust artifacts.