Chokri Belaid knew that his life was at risk. The secretary general of Tunisia's Unified Democratic Nationalist Party, and a key member of the secular opposition front, had been receiving death threats for months. When he was killed yesterday outside his home in Tunis, however, the fear was that it was the country that was now in danger.
Tunisia has been spared most, but by no means all, of the violence that has followed the Arab uprisings. Many of the country's street clashes have been sparked by Islamist groups directing their anger against broadcast stations, art exhibitions and the like, which they deem to violate their strict religious interpretation. The state, also, has often been guilty of using excessive force in dealing with demonstrations.
Mr Belaid was an outspoken critic of the Islamist groups, including the dominant Ennahda Party, which is considered to be more moderate. Suspicion has already fallen on Mr Belaid's political adversaries, and a quickly organised protest in the capital yesterday blamed the government for his death while several Ennahda offices were attacked across the country. In recent days, Mr Belaid had even accused Ennahda of endorsing political assassinations, which will fuel speculation.
But any conclusion at this point is just that - pure speculation. Mr Belaid made enemies in post-Ben Ali Tunisia, but that does not necessarily meant that his adversaries are murderers. All sides must wait for a full investigation before drawing their conclusions.
The government - and by extension Ennahda, which holds the most seats of any party in parliament - will be tested by the integrity of that investigation. Mr Belaid was a fierce political partisan; his murder, however, is an attack on the entire country. As politicians in Tunis struggle to cobble together a more inclusive coalition, political violence undermines every effort at compromise and threatens the basic security of the state.
And the entire country appeared shaken yesterday. Tunisia has not seen the scale of violence of Egypt's protests, the wars felt by Syria and Libya, or the assassinations to which Lebanon has become inured. The thought that Mr Belaid's death could be the first among many is frightening indeed in this new-found democracy. The response by Prime Minister Hamadi Jebali, a member of Ennahda, was to call the killing "the assassination of the revolution".
Tunisia's leaders have to treat this murder as a crime, rather than an escalation of their partisan differences. At stake is the country, not just the revolution.