Accusations that the brother of former Mexican president Carlos Salinas masterminded high-level assassinations promise to change the country's political establishment forever. Government sources tell TIME Mexico City bureau chief Laura Lopez that Raul Salinas de Gortari, who was arrested Tuesday, may also be charged with complicity in the March, 1994 assassination of former presidential candidate Luis Donaldo Colosio. By acting swiftly to arrest the prominent suspect, and promising today that dozens more heads will roll, President Ernesto Zedillo, who succeeded Salinas last year, "has ended impunity in Mexico which goes back centuries," says Lopez. "He has broken the tradition of an incoming president protecting the sins of an outgoing president." Now, Lopez reports, investigators are chasing leads that have already netted the arrest of one undersecretary and could implicate dozens more officials -- some with reputed ties to drug lords. "The investigators fear for their lives," Lopez says. Last night, prosecutors charged Raul Salinas de Gortari, whose brother Carlos left office in December, with arranging the September killing of the ruling PRI party's No. 2 man, Jose Francisco Ruiz Massieu.