MEXICO CITY — A woman who joined with other activists to seek relatives who have disappeared in Mexico’s wave of violence has been murdered in the northern border state of Sonora.

The state prosecutor’s office vowed that “justice will be done” in the case of Gladys Aranza Ramos Gurrola, a member of the Mothers and Searching Warriors of Sonora. She was found shot to death near midnight Thursday at her home in the municipality of Guaymas.

The 28-year-old woman has been searching for her husband, who disappeared in December 2020.

The prosecutor’s office described her as “always brave, active, enthusiastic and showing solidarity” in the group’s searches. It said it is investigating whether her activities could have played a role in the shooting.

The federal government said on Monday that 68 human rights or environmental activists have been killed since President Andrés Manuel López Obrador took office in December 2018. She would be the 69th.

Mexico has reported more than 87,800 missing people since 2006, when then-President Felipe Calderón expanded the country’s battle against drug cartels.

For years, groups of relatives of the disappeared have joined together to make their own searches for the missing, sometimes finding mass graves that authorities then have excavated.