GUNMEN shot dead Argentine folk singer Facundo Cabral on Saturday as his car made its way to the airport in Guatemala City, police said. A motive for the killing of one of Latin America's best-known folk singers remained unclear. The singer's agent was also shot and is in stable condition in the hospital, said police spokesman Donald Gonzalez. In Guatemala on a Latin American tour, Cabral, 74, left his hotel at 5:40 a.m. in a white SUV for an eight-minute ride to the airport. Gunmen attacked the SUV -- at least 20 bullet holes could be seen on the Range Rover. Nothing was reported stolen from the vehicle, government spokesman Ronaldo Robles said. Police found a brown Hyundai Santa Fe nearby containing bullet-proof vests and AK-47 magazines. Guatemalan President Alvaro Colom declared three days of national mourning. His government said an investigation has been launched but, at this point, that it was too early to say whether Cabral was the victim of a robbery or a direct attack. "As a country, we are saddened by the cowardly attack against those who will live on in memory -- singing about life, happiness and love," the government said in a statement. Guatemalan Nobel Peace Prize winner Rigoberta Menchu traveled to the site of the attack, where she wept and said the singer had died "for his ideals," according to Notimex, the state-run news agency in Mexico. CNN