Police in the US state of Ohio arrested a husband and wife and their two sons Tuesday over the "meticulously planned" murder of eight people - seven members of the same family and a fiancee.
George Wagner III, Angela Wagner and their sons George Wagner IV and Edward Wagner are accused of carrying out the April 2016 massacre in Peebles, a rural village 80 miles (130 kilometers) east of Cincinnati.
"Members of one family conspired, planned, carried out and then allegedly covered up their violent act to wipe out members of another family," Pike County Sheriff Charles Reader told a news conference.
Ohio Attorney General Mike DeWine said the motive was related to child custody, without clarifying further.
Police found seven bodies, each with a bullet to the head, in three separate homes, and an eighth at a separate site. Many were killed in their sleep.
The seven family members killed were Christopher Rhoden Sr., 40; Christopher Rhoden Jr., 16; Clarence "Frankie" Rhoden, 20; Dana Rhoden, 37; Gary Rhoden, 38; Hanna Rhoden, 19; and Kenneth Rhoden, 44.
The other victim, 20-year-old Hannah "Hazel" Gilley, was engaged to Clarence Rhoden.
The shooters spared three young children: a newborn baby found lying next to her dead mother, as well as two others who were six months and three years old.
Officials accused the Wagners of an elaborate cover-up, including tampering with cell phones and security camera footage.
"They did this quickly, coldly, calmly and very carefully. But not carefully enough," Reader said.
"They left traces. They left a trail: The parts to build a silencer, the forged documents, the cameras, the cellphones, all that they tampered with, and the lies, all the lies they told us."
Each of the suspects faces eight counts of aggravated murder.
If convicted, they could get the death penalty.
Police also arrested Rita Newcomb, identified as Angela Wagner's mother, and Fredericka Wagner, George Wagner III's mother.
They are accused of helping with the cover-up.
The killings sent shockwaves through the community, located in an economically distressed region of around 28,000 people that is home to an abandoned uranium plant.