Updated

A mother who spent years searching for her missing daughter in northern Mexico and organized others to look for their disappeared relatives has been slain.

The group Citizen Community in Search of the Disappeared in Tamaulipas, to which Miriam Rodriguez belonged, says she was shot to death at her home Wednesday night in the town of San Fernando in Tamaulipas state.

San Fernando is about 90 miles south of Brownsville, Texas, and is a critical point on drug- and migrant-smuggling routes to the border.

The statement says that Rodriguez's tireless search had eventually led to her daughter's remains in an unmarked grave and she told authorities who was responsible.

Tamaulipas state Gov. Francisco Cabeza de Vaca went on Twitter to condemn Rodriguez's killing and promise justice.