By: Stephan F. Jackson A PROMINENT LEFT-wing newspaper editor was murdered in Bogot? Aug. 9, prompting indignation among human rights groups appalled at Colombia's surging violence. Manuel Cepeda Vargas, 64, the editor for 15 years of Voz, or Voice, and an internationally known communist senator in Colombia's legislature, was shot in the head while driving into Bogot? from his home in the suburbs in the afternoon. The killer was unknown. According to a witness, the gunman, a passenger in another vehicle that drove alongside Cepeda's, aimed a gun through an open window and opened fire. Some 50 years old, the weekly Voz has a circulation of approximately 15,000 and about 20 employees. An outspoken voice of the left, the paper is the unofficial organ of the Patriotic Union, a legal Communist Party group founded in 1980 to work within the system, and has denounced human rights violations by Colombian police and the military. The PU, however, is loosely affiliated with an underground Marxist terrorist group, which has fomented violence that has led to the deaths of about 120 civilians and police recently. No one claimed credit for Cepeda's murder, but police suspect a new right-wing, paramilitary group, Colombia Without Guerrillas, whose purpose is exterminating violent communists and their supporters. Cepeda was well known as the Communist Party's primary liaison in the legislature and was a leader in trying to bring the violent Revolutionary Armed Forces of Colombia to abandon terrorism and to join the political process. "The government never offered him protection," claimed Cepeda's son, Ivan Cepeda Vargas. "The military assassinated Manuel Cepeda with government complicity," chanted a crowd of PU members who surrounded the dead editor's bloody vehicle and during an impromptu rally. A regional human rights group, the Andean Commission on Jurists, said Colombia suffers about 10 political killings a day, and few are solved. Statistics show a murder every 20 minutes, and 97% of them go unpunished. There is no death penalty for murder in Colombia. "The situation is appalling," said Gustavo Gallon, director of the Colombian chapter of the Andean Commission. "The problem is known worldwide, but the government has not done anything. The killings show the severity of the judicial and human rights situation in Colombia."