The police delivered another blow to the Medellin cocaine trafficking ring by killing the man who they said masterminded a 10-month campaign that has killed hundreds of people, officials said today.

The suspect, Juan Jairo Arias Tascon, was killed Wednesday night in a shootout with members of Colombia's Elite Police Corps, a group specially trained to fight drug traffickers.

A police spokeswoman said the authorities had been tipped off to Mr. Arias's whereabouts, an apartment in an exclusive suburb of Medellin, the headquarters for the most violent of the country's two major cocaine trafficking rings.

Shootout, Then a Car Bomb

Mr. Arias resisted arrest and the police shot and killed him, the spokeswoman said. She added that neither the officers nor a woman and a 6-month-old baby also in the apartment were harmed.