A dozen police officers investigating the beheadings of 10 people were killed in an ambush in southern Mexico. Another 11 officers were injured. The officers were traveling in six patrol cars searching for the bodies of seven men and three women whose heads were found dumped outside a slaughterhouse in Guerrero state, AP reports. The killings are believed to be the work of the Knights Templar cartel, which is battling La Familia for control of the state's drug routes. Pope Benedict XVI arrives in Mexico this Friday, and he is expected to comment on the country's drug-related violence.