Two years after he surrendered to Colombian authorities, one of the country's most infamous drug lords was shot to death this morning as he played soccer in a prison yard outside Cali, officials said.

Helmer "Pacho" Herrera, 47, was considered one of the top three members of the notorious Cali drug cartel, which once controlled up to 80 percent of the world's cocaine trade.

Herrera was killed at about 9:30 a.m. by a man who entered the maximum-security Palmira prison east of Cali posing as a lawyer, according to a spokesman for the National Prison Institute. The assassin fired six rounds from a 9mm pistol into Herrera's head and abdomen during a break in the soccer game, the spokesman said.

Herrera died shortly afterward at a nearby hospital, officials said.

Prison guards immediately seized the gunman, who had identified himself before the attack as a lawyer named Rafael Angel Uribe Serna, a prison spokesman said. Officials said they are investigating whether prison guards collaborated in the killing.

Herrera eluded scores of raids by Colombian police before surrendering in Cali in September 1996. In 1998, a judge sentenced him to six years and eight months in prison for drug trafficking and ordered him to pay a $1 million fine. In July, Herrera turned in his half brother, Jose Manuel Herrera, on drug-related charges in return for an undisclosed sentence reduction.

Helmer Herrera's relatively light sentence was condemned by U.S. officials, who had sought to bring him to trial in the United States for his role in directing cocaine distribution and money laundering activities in the New York City area. In 1996, Attorney General Janet Reno asked Colombia to send Herrera to the United States, but Colombia's extradition law applies only to crimes committed after it was enacted in 1997, when Herrera was already in jail.