Villavicencio, a vocal critic of corruption and organized crime, was killed leaving an evening campaign event at an education facility in northern Quito.
A seventh suspect who died on Wednesday from wounds sustained in a shootout with police was also Colombian.
The involvement of Colombian nationals in the murder is reminiscent of the 2021 killing of Haiti’s deceased President Jovenel Moise, who was assassinated in his home by a group which included 26 Colombians and two Haitian-Americans.