A state investigator and six other men were arrested for allegedly stabbing and shooting to death six members of a family in connection with an extortion bid, police said.
Police officer Alejandro Lopez sent gunmen to the family's house in Ciudad Guzman, in the western state of Jalisco, last week to demand USD 100,000, state prosecutors alleged in a statement.
Lopez, a Jalisco investigator, then showed up at the house pretending to make a casual visit, prosecutors said. When he encountered the gunmen, he allegedly encouraged the family to turn over the money so the assailants would go away.
Lopez, who had helped investigate the kidnapping of the family's teenage son in April, is believed to have staged the robbery after becoming aware of the family's access to large sums of money, prosecutors said.
Investigators said they found USD 100,000 in Lopez's home.
The family members were killed when they figured out that Lopez was behind the assault, authorities said.
Their bodies were found Wednesday last in their house, which was previously owned by Mexican Agriculture Secretary Alberto Cardenas, the prosecutor's office said. They had been dead for at least a day and a half.
Four of the victims, including two children, were shot in the head. A teenage boy had his throat slashed and his mother was asphyxiated with a plastic bag.
Cardenas has said the family bought the house from him and two months ago because they thought they would be safer there after the boy's kidnapping.