In the Mexican border town of San Fernando, Tamaulipas, one mother took justice into her own hands after suffering an unimaginable loss. Miriam Elizabeth Rodríguez Martínez launched a one-woman crusade against the powerful Los Zetas drug cartel after her daughter, Karen, was kidnapped and murdered in 2012.

Though Miriam paid the ransom, Karen was still killed, and her remains weren’t discovered until two years later in 2014. Unwilling to let her daughter’s killers walk free, Miriam began her own investigation—using disguises, fake identification, and undercover surveillance. She even once held a cartel member at gunpoint until police arrived. Her efforts helped bring at least ten of Karen’s murderers to justice.

But her heroic fight came at a heartbreaking cost. On Mother’s Day in 2017, Miriam was shot and killed outside her home.

Today, her son Luis continues her mission, leading a collective of more than 600 families searching for their missing loved ones.

Miriam’s story remains a powerful testament to a mother’s love—and to the strength and resolve it takes to stand up to some of the world’s most ruthless criminals.