Cartel gunmen have murdered a woman who led the search for her daughter’s remains and other victims in northern Mexico. The gunmen killed her on the day Mexico celebrates Mother’s Day.

Mexican authorities have confirmed the murder of Miriam Elizabeth Rodriguez Martinez, on the night of May 10 in the city of San Fernando, Tamaulipas. As Breitbart Texas reported, San Fernando has a long history of being a stronghold of Los Zetas Cartel, one of the most ruthless criminal organizations in Mexico. Two former Tamaulipas governors are wanted by the U.S. Department of Justice on money laundering charges for their roles as surrogates of the Los Zetas. One of those politicians is also wanted on multiple drug trafficking and conspiracy charges.

Los Zetas have been behind the execution of 72 Central American immigrants who were murdered in San Fernando in an apparent show of force. The same criminal organization has been singled out as being behind the disappearance of hundreds of victims from San Fernando. In 2011, close to 200 victims were discovered in shallow graves in rural areas near San Fernando. At the time, authorities revealed that the victims may have been kidnapped off passenger buses or may have been motorists traveling one of the state’s main highways near the city.

In 2012, cartel gunmen kidnapped the daughter of Miriam Elizabeth Rodriguez Martinez. Despite the lack of cooperation from the Mexican federal government, the activist formed a support group that focused on pressuring the government and helping locate missing victims. Rodriguez Martinez was able to locate the mass grave where the gunmen buried her daughter’s body. Through her work, Martinez was able to contribute to the arrest of nine Los Zetas gunmen directly responsible for her daughter’s kidnapping.

According to the Tamaulipas government, Rodriguez Martinez requested government protection after learning that Enrique Yoel Rubio, the main suspect behind her daughter’s murder, was named among the dozens of inmates who broke out of a state prison earlier this year. As Breitbart Texas reported in May, at least 29 members of Los Zetas used a tunnel to break out of the state prison in Ciudad Victoria. The breakout came after the cartel was undergoing an internal fight for territorial control.

While federal authorities ignored Rodriguez’s cry for help, state authorities provided her with a series of police checkups at her home. Information provided to Breitbart Texas by Tamaulipas authorities revealed that Rubio had been arrested shortly after the breakout and has remained behind bars since.

Despite state cops checking in on Rodriguez, unknown cartel gunmen were able to carry out the assassination earlier this week. State officials issued a strong condemnation and claimed they would not let the murder go unsolved.

Ildefonso Ortiz is an award-winning journalist with Breitbart Texas. He co-founded the Cartel Chronicles project with Brandon Darby and Stephen K. Bannon. You can follow him on Twitter and on Facebook.

Brandon Darby is managing director and editor-in-chief of Breitbart Texas. He co-founded the Cartel Chronicles project with Ildefonso Ortiz and Stephen K. Bannon. Follow him on Twitter and Facebook. He can be contacted at bdarby@breitbart.com.