Former Argentina international Federico Aramburu was killed in Paris on Saturday morning after an altercation in a bar.
The incident took place around 6am local time on the boulevard Saint-Germain on the Left Bank, after a dispute between two groups.
The groups separated but the alleged perpetrators "returned shortly after with a vehicle and fired shots," said a police source.
"Several bullet marks" were found on the spot, added a source close to the investigation and Aramburu died on the spot as a result of his injuries.
A murder investigation has been opened.
The suspects were still being sought late Saturday morning, according to sources close to the case.
One of Aramburu's group, a former Biarritz team-mate who wished to remain anonymous, said they were in a well-known bar, the Mabillon, ending their night out with hamburgers.
"There was an altercation, as there can be at the end of the evening," the source said. "It was settled but the men came back and fired at Aramburu, who took three bullets."
Aramburu was 42 years old. He was a back who won 22 caps for his country and played in the 2007 World Cup in France, scoring a try as the Pumas beat the hosts in the third-place playoff.
He played club rugby in France for Biarritz, Perpignan and Dax.
He won the top 14 twice with Biarritz and later sat on the club's board of directors.
Since his retirement from sport, he had lived in Biarritz and worked for a tourism company.