Chokri Belaid, a leader of a Tunisian opposition alliance, had always been highly critical of the ruling Islamist party, Ennahda. He had accused it of looking the other way when extremists attacked members of secular political parties.
He did so again on Tuesday evening in Tunis, when he appeared on the Nessma TV channel. "There are groups inside Ennahda inciting violence," he said. "All those who oppose Ennahda become targets of violence."
Only a few hours later, early on Wednesday morning, Mr. Belaid, who often claimed that he had received death threats, was assassinated outside his house in Tunis. A government minister said Mr. Belaid, 47, was shot at point-bank range in the head and neck by a gunman, who took off on a motorcycle with an accomplice. Mr. Belaid died shortly after in a nearby hospital.
The assassination triggered demonstrations in central Tunis at a time when political tensions were already running high in the country. There is now no doubt that Tunisia's transition to a stable and all-inclusive democracy, a process which had been considered a model for other Arab Spring countries, is running into trouble.
The domestic and international backlash against the assassination was so swift and fierce that Tunisian Prime Minister Hamadi Jebali dissolved his government Wednesday night. It will be replaced by a non-partisan government of technocrats who will be "limited to managing the affairs of the country until elections are held in the shortest possible time," he said on national TV.
"The murder of Belaid is a political assassination and the assassination of the Tunisian revolution," he said earlier.
A Tunisian diplomat, who did not want to be identified, cheered the news of the end of the Ennahda government, which he said had been discredited by the wave of violence in recent months. "This tragedy has the potential to turn things around for the better," he said.
Earlier in the day, thousands of angry protesters filled Avenue Habib Bourguiba in central Tunis, the site of the mass protests that led to the ouster of Tunisia dictator Zine El Abidine Ben Ali during the revolution. The protesters were broken up in the afternoon by riot police equipped with batons and tear-gas canisters, which were flung into the crowds. Some of the protesters shouted "No to Ennahda" or "Degage," the French term for "Get out," the chant directed at Mr. Ben Ali in the dying days of his rule.
Several Ennahda offices in Tunis and other cities were attacked; a few were reportedly set on fire. Unions called for a general strike on Thursday.
While Mr. Belaid's death is the first political assassination since Mr. Ben Ali fled to Saudi Arabia on Jan. 14, 2011, there has been a spate of violent attacks on opposition party members and members of secular society, ranging from artists and journalists to prostitutes and filmmakers. Some of the attacks have turned deadly.
The opposition parties blame Ennahda for tolerating the violence or not reacting quickly enough to stop it, even though Ennahda officials have always insisted violent acts will be punished. The identity of Mr. Belaid's killer was not known by Wednesday night, but many Tunisians suspected it was the work of one of the Leagues for the Protection of the Revolution.
The leagues began as neighbourhood protection squads during the violent days of the revolution and were were legalized by the government last autumn. The opposition claims they are, in effect, Ennahda's enforcers and will harass or attack any person or group they consider a threat to Islamist authority.
"I was angry and shocked and could just not believe the news of Chokri's assassination," said Kamel Labidi, the president of the national committee for the reform of the media and communications industry. "The government has taken no significant steps to bring the leagues to justice."
Mr. Belaid's brother, Abdel Majid, blamed the Islamist government for the spate of violence that killed Mr. Belaid. "Rachid Ghannouchi better not come to my brother's funeral," he told the Tunisia Live news site, referring to the Ennahda leader.
Ennahda members were quick to condemn the assassination. Mr. Ghannouchi told the Associated Press that Mr. Belaid's death was an "ignoble act" and that those who wanted him dead are "parties whose interests are threatened by the revolution and the democratic transition."
A statement issued by the U.S. embassy in Tunis, which was attacked on Sept. 14 by a large group of extremists, resulting in the deaths of four attackers, said: "There is no justification for this outrageous and cowardly act, and political violence has no place in Tunisia's democratic transition."
Mr. Belaid was a lawyer who worked on human-rights cases. He was not an elected member of the National Assembly but was a leader of the leftist alliance of parties known as the Popular Front.
Mr. Labidi, who knew Mr. Belaid, said he was famous because he never hesitated to go after the Islamist government. "He was provocative and was one of the most critical voices among the opposition," he said. "He didn't like the attempts to impose a new way of life on Tunisians, a way of life that he considered inspired by radical Islam."
Mr. Belaid's death was condemned by European political leaders. They consider Tunisia, which is close to Italy, part of their "neighbourhood" and hope that its transition to a stable democracy, if it happens, will inspire other Arab Spring countries.
"This murder deprives Tunisia of one of its most courageous and free voices," said French President François Hollande. "Belaid was committed throughout his political life to the fight for freedom, tolerance and respect for human rights."