Argentine singer Facundo Cabral, one of the stars of Latin American folk music, was shot dead in Guatemala City early on Saturday when unidentified gunmen riddled his car with bullets, authorities said, according to Reuters. Cabral, who rose to fame in the 1970s as a protest singer, was killed along with his driver as they made their way to the city's airport before dawn, police said. A spokesman for Guatemalan president Alvaro Colom said Cabral's vehicle was peppered with 18 bullets and Colom himself vowed to take swift action against the perpetrators. "We will find these criminals and bring them to justice," Colom told Argentine radio. Argentine television stations interrupted broadcasts with news of the 74-year old singer's death. Colom said he spoke to Argentine President Cristina Fernandez to offer his condolences for the killing, the motive for which was unclear. A firefighter at the scene said colleagues saw black vehicles pull up and open fire on Cabral's white Range Rover and the beige Chevrolet Tahoe accompanying the singer. Guatemala, one of the poorest countries in the region, has one of Latin America's highest murder rates. Colom has struggled to contain the violence and Cabral's murder is an embarrassment to the president just two months before a first round of presidential elections which polls show his center-left National Union of Hope party (UNE) may lose. The president's office said authorities were investigating whether the shooting was robbery-related or a targeted attack. Enrique Vaca Narvaja, Argentina's consul to Guatemala, told Argentine television that Cabral's driver was a businessman named Henry Farina and it was unclear who was the target. "We don't know if the attack was against the businessman or against Facundo, this is part of the investigation," he said. The second car, a security detail, was also sprayed with bullets, causing serious injury to at least one person. A large crowd of onlookers quickly gathered at the crime scene, which was next to a fire station a few hundred meters away from the turn-off for the airport. Some shouted angrily as police and army cordoned off a large stretch of the road. "We want justice," cried one man. HUMBLE ORIGINS Cabral's death sparked sorrow among his fans and Argentina's Foreign Minister Hector Timerman paid tribute to the singer on his Twitter account. "The murder of Facundo Cabral in Guatemala brings us great sadness," he wrote. "Adios amigo!" Rising from humble origins, the outspoken Cabral was best known for his 1970 song "No Soy De Aqui, Ni Soy De Alla," (I'm Not From Here, I'm Not From There Either) which was covered by many other artists including Julio Iglesias. Cabral went into exile in Mexico during Argentina's 1976-1983 military dictatorship. His songs later turned more spiritual and he continued to fill concert halls across Latin America. He had been in the Central American country on tour. Edgar Palacios, 54, a local fan, was distraught at Cabral's death and said the singer would not be forgotten. "Facundo Cabral died but his music will never die, just like John Lennon died but his music never died," he said. "Cabral wasn't just from one country. He was a universal man." Others said the killing showed the criminal malaise afflicting Guatemala, which has been racked by incursions from Mexican drug gangs, notably the brutal Zetas cartel. Rigoberta Menchu, a rights' activist for indigenous peoples in the country who won a Nobel Peace prize in 1992, said Cabral's murder was just one of many in Guatemala. "This is a well planned crime," she told reporters at the scene. "International criminals base themselves in Guatemala because they know they can get away with acts like this." Menchu is among the candidates standing for the presidency, which voter surveys suggest could lead to the UNE's ousting. A first round of voting is due on Sept. 11 and Colom himself is barred by law from seeking re-election. The UNE's main candidate, Colom's ex-wife Sandra Torres, had her bid to run for office blocked by a Guatemalan court in late June. Polls have shown her trailing the main right-wing candidate, former general Otto Perez, by a wide margin.