While the assailants hadn't been identified, Arturo Sandoval, a spokesman for the Chihuahua state attorney general's office, said the incident may be linked to local drug lords, CNN reported.
Benjamin LeBaron and his brother-in-law, Luis Widmar, were beaten and shot to death after armed men stormed their Galeana home Tuesday, officials said.
Sandoval said a note was found on LeBaron's body, but could not confirm the message, CNN said. However, local media reported the note suggested the killings were in retaliation for the capture of 25 drug suspects in a nearby town.
LeBaron's younger brother, Eric, was kidnapped in May and later returned unharmed, prompting LeBaron to become an outspoken anti-crime activist. The LeBaron brothers belonged to the "Community of LeBaron" in Galeana,CNN said.
"There are no leaders here, or we are all leaders," LeBaron's brother, Julian LeBaron, told KINT, El Paso, Texas. "If they kill my brother, another three will take his place; and if they kill us, another hundred will take their place. We are not giving up. No way."