(Reuters) - Four members of a family face the death penalty after a grand jury charged them with the April 2016 execution-style shooting deaths of eight members of another rural Ohio family, Ohio Attorney General Mike DeWine announced on Tuesday.

Four members of the Wagner family were charged with murdering seven members of the Rhoden family and a fiancée of one of the victims, DeWine told a news conference in Pike County, where the killings took place.

There was an extensive plot to kill in four different crime scenes and a cover-up that included the suspects temporarily moving to Alaska and returning to Ohio in the spring, DeWine said.

The four Wagners “clearly have been the prime suspects for some time,” DeWine said.

DeWine, elected Ohio governor last week, did not pinpoint a motive but suggested the primary intent of the killers was custody of a small child, whose father was a Wagner and mother a Rhoden.

Investigators found evidence of illegal drug activity, cockfighting and the possible involvement of a Mexican drug cartel.

DeWine suggested the bigger motive was child custody.

“There certainly was obsession with custody, obsession with control of children,” said DeWine, adding, “This is just the most bizarre story I’ve ever seen in being involved in law enforcement.”

An attorney reportedly representing the Wagners did not immediately respond to a request for comment.

George “Billy” Wagner III, 47, his wife Angela Wagner, 48, and their two sons, George Wagner IV, 27, and Edward “Jake” Wagner, 26 are each charged with eight counts of aggravated murder.

Also arrested on Tuesday in an alleged cover-up were Angela Wagner’s mother, Rita Newcomb, 65, and Billy Wagner’s mother, Fredericka Wagner, 76, state officials and local media said.

Three children including a 6-month-old and a 3-year-old survived the killings. One woman was killed while sleeping with her 5-day-old baby.

The victims included Christopher Rhoden Sr., 40; his ex-wife, Dana Rhoden, 37; and their three children, Hanna, 19, Christopher Jr., 16, and Clarence, 20.

Three other victims were Christopher Sr.’s brother, Kenneth Rhoden, 44; a cousin, Gary Rhoden, 38; and Clarence Rhoden’s girlfriend, Hannah Gilley, 20.

Pike County Sheriff Charles Reader said the six suspects were being held at different locations in Ohio and Kentucky. Arraignments were expected in the coming days, a prosecutor said.

Pike County is in the Appalachia foothills about 95 miles (150 km) east of Cincinnati.