Argentine legislator Héctor Olivares died three days after being seriously wounded in a gun attack that killed a provincial official, a Senate official said Sunday.

Acting Senate president Federico Pinedo said Olivares died of his wounds earlier in the day.

"A great pain the death of Deputy Olivares," Pinedo tweeted.

ARGENTINE LAWMAKER FIGHTING FOR HIS LIFE AFTER BEING AMBUSHED BY GUNMEN

President Mauricio Macri decreed a 48-hour period of national mourning.

FILE - In this May 18, 2016 file photo provided by the Nation's Honorable Chamber of Deputies, lawmaker Hector Olivares attends a congressional commission session in Buenos Aires, Argentina. Argentine Senate President Federico Pinedo confirmed on May 12, 2019 that Olivares died after he was seriously injured in a May 9 shooting near the congressional building in Buenos Aires. (Nation's Honorable Chamber of Deputies, HCDN via AP, File)

At least six people have been detained in what has been described as a "mafia-style" attack Thursday that shocked Argentines. Officials have said two gunmen in a parked car shot wounded Olivares and killed Miguel Marcelo Yadón near the country's congressional building in Buenos Aires.

Olivares, a member of the pro-government Radical Civic Union party, represented La Rioja province in the Chamber of Deputies, the lower house of congress. Yadón worked for La Rioja's federal electric transportation system.

Evidence tent markers dot the crime scene where lawmaker Hector Olivares was seriously injured and another man was killed after they were shot at from a parked car near Congress in Buenos Aires, Argentina, Thursday, May 9, 2019. (AP Photo/Natacha Pisarenko)

Authorities have said investigators are working to determine a motive.