The shootings Saturday night in the state of Tabasco stunned an oil-rich part of Mexico that has not experienced the same level of drug-related warfare common elsewhere in the country, despite its position of strategic importance to traffickers.
The killing of police officer Carlos Reyes Lopez came days after police in Tabasco captured four gunmen and left one suspect dead. Although some speculate that the motive was retaliation, the state prosecutor's office also suggested that a personal dispute involving the Reyes Lopez family might have been behind the attack.
Reyes Lopez and 10 members of his family, including a 2-year-old nephew, were killed. The 12th victim was a fruit vendor who was there to deliver frozen strawberries. No arrests were reported.
"They killed my brother Carlos, his whole family, my son, my mother. . . . They killed everyone," said a sobbing survivor identified as a sister of the dead officer and mother of the 2-year-old, according to an account in Tabasco Hoy newspaper.
The newspaper said Reyes Lopez was a member of an elite police agency formed last year amid efforts to rid public security forces of rampant corruption. Members of the new force had to pass rigorous exams, drug testing and additional vetting procedures.
In other violence, gunmen using grenades and assault rifles attacked, for the fourth time in two days, a police station in the state of Michoacan. A police officer was injured in Saturday night's incident, adding to two other officers and eight civilians who have been wounded in the string of attacks.
Michoacan is the home state of President Felipe Calderon, and a drug mafia called La Familia has been making inroads in parts of the state.
In Mexico City, authorities discovered the decapitated bodies of two women in the trunk of a parked car. The heads were in a cooler in the car's back seat, newspapers reported Sunday. Seven people were reported killed in a shootout at a restaurant in Jalisco state and five at a wake in Durango state.
Also on Sunday, colleagues reported the killing of a photographer for a newspaper in the town of Iguala, in Guerrero state. And the Mexican navy announced the discovery and confiscation of 7 tons of cocaine on a ship off the Pacific coast.