With the death of Oswaldo Payá, a key leader of the Cuban democratic opposition, Cuba has suffered what the writer Yoani Sánchez called “a dramatic loss for its present and an irreplaceable loss for its future.” The circumstances surrounding Payá’s death Sunday have sparked controversy similar to that caused in October by the death of Laura Pollán, the leader of the much-acclaimed Ladies in White, just weeks after she was attacked at a protest march by a government supporter.

The Cuban government said that Payá died in a traffic accident near the city of Bayamo when his car slammed into a tree, killing him and another passenger and injuring two others. But Payá’s daughter, Rosa María Payá, immediately challenged that version, saying that the family had received information from the survivors that their car was repeatedly rammed by another vehicle. “So we think it’s not an accident,” she said, according to CNN en Español. “They wanted to do harm and then ended up killing my father.”

The family also said that Oswaldo Payá was targeted in a similar incident two weeks earlier in Havana. In retrospect, they now see that incident as a warning from the regime.

Why would the Cuban government regard Payá as enough of a threat to want him killed? He was one of the most prominent opponents of the Cuban dictatorship, a Catholic activist who founded the Christian Liberation Movement in 1988. He is best known for the Varela Project, a petition drive he launched in 2002 that called for free elections and other rights. That angered the Cuban government, which responded by forcing through the National Assembly a constitutional amendment making the communist system in Cuba irrevocable. It followed that with the 2003 “Black Spring,” arresting 75 of the most prominent Cuban activists that March.

But the government didn’t arrest Payá, because of the international renown that he had achieved. The European Parliament awarded him its Sakharov Prize for Freedom of Thought in 2002; that year he was also nominated for the Nobel Peace Prize by hundreds of parliamentarians in a campaign led by his friend Vaclav Havel, the Czech Republic president. Unlike Aung San Suu Kyi of Burma and Liu Xiaobo of China, for whom Havel also campaigned, Payá never received the Nobel Prize.

But he was an activist in the same mold — a centrist within the opposition, committed to nonviolence and reconciliation. Pay opposed the U.S. embargo against Cuba, for which he was criticized by some opponents of the Castro regime.

Although other activists had replaced Payá in recent years at the cutting edge of the Cuban democracy movement, he recently provoked the government on two issues of great sensitivity.

In May, Payá broke a long silence when he sharply criticized an article in a lay Catholic publication that had defended the dialogue of the archbishop of Havana, Cardinal Jaime Ortega, with the regime and had attacked the cardinal’s critics.

Payá accused the article’s authors of seeking to create “an artificial confrontation between the opposition and the church,” calling them “political commissars” who were asking “for a vote of confidence for Raúl Castro’s government.”