Hundreds gathered in San Andres Larrainzar, Chiapas, to mourn Catholic priest and activist Marcelo Pérez, who was killed by gunmen after celebrating Mass.

Pérez, 50, advocated for Indigenous peoples and farm laborers, and often received threats from organized crime groups in the violence-ridden state.

Despite warnings, the government did not provide protection for him.

Human rights advocates blame his death on the state’s escalating violence, fueled by drug cartels battling for control of the region, CBS News has reported.

Authorities are investigating, but no details on the killers have been released.

Written by B.C. Begley