BOGOTA, Colombia (AP) — A onetime leading cocaine trafficker who gained notoriety a decade ago for testifying against Medellin cartel member Fabio Ochoa in a U.S. courtroom has been slain by gunmen in his homeland

Two hit men on motorcycles killed Alejandro Bernal and another man in the town of Sopo north of Bogota on Nov. 30 while they were engaged in real estate and luxury automobile deals, the national police director, Gen. Jose Leon told, The Associated Press on Tuesday.

Bernal, who was in his mid-50s, had been in Colombia for about a month, Leon said. U.S. Bureau of Prison records say he was released from federal prison in April 2009.

Leon said police investigating the killing were operating with two theories: Bernal was killed in retaliation for cooperating with U.S. authorities, or he was trying to get back into the drug business.

Bernal was considered a major trafficker by U.S. and Colombian authorities when they arrested him in 1999 along with more than 30 other alleged associates, including Ochoa, in what was dubbed "Operation Millennium."

Prosecutors said Bernal was the brains of the operation, Ochoa the brawn.

In testimony in U.S. court, Bernal described Ochoa as a friend since their initial cocaine dealings in 1983. He said he later delivered planeloads of cocaine to the late Mexican drug king Amado Carrillo Fuentes in the late 1980s.

U.S. prosecutors called Bernal's Bogota office of the late 1990s "the Wal-Mart of drug trafficking" and said his organization smuggled 30 tons of cocaine a month to the United States. They said Bernal served as a broker, connecting Colombian producers with world-class smugglers who used everything from frozen fruit pulp to billiard tables to smuggle the drug into the United States.

Bernal and most of his co-defendants cooperated with U.S. prosecutors.

At a sentencing hearing in 2003, Bernal's attorney, Ruben Oliva, acknowledged the risk of reprisal that Bernal faced for cooperating with U.S. investigators against Ochoa, whose family is legendary in Colombia for its place in the Medellin cartel alongside the late Pablo Escobar.

"He's painted a big target on himself, his wife, his family and his sister through his cooperation with the government," Oliva said.

Later that year, Ochoa was sentenced to 30 years in prison.

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Associated Press writer Frank Bajak contributed to this report.