WAVERLY (AP) — A man on trial in the 2016 slayings of eight current and prospective members of another family in southern Ohio testified Wednesday that he had no idea his relatives planned to kill the victims and that he would have taken action to prevent the slayings had he known about such a plan.

George Wagner IV, 31, took the stand in Pike County and denied any knowledge of his family’s involvement in the slayings of seven members of the Rhoden family and one future member of the family, which authorities have said stemmed from a custody dispute.

“I never would have believed my family would be capable of doing something of this magnitude,” said George Wagner IV, whose mother and brother have pleaded guilty to roles in the case and whose father awaits trial. “Theft is one thing. Murder is an entirely different thing.”

Asked by his attorney what he would have done had he known, he said “I would have never let it happen. One way or another, I would not have let it happen.”

Special prosecutor Angela Canepa has not accused George Wagner IV of shooting anyone but has alleged that he took part in planning, carrying out and covering up “one of the most heinous crimes in Ohio history.” The defense has argued that George Wagner IV is not like the rest of his family and had nothing to do with the killings.

Canepa has alleged that George Wagner IV was with his brother and his father when they drove to three separate locations where all eight victims were killed, went inside with the pair and helped his brother move two of the bodies.

George Wagner IV testified that he was at home sleeping on the night of the murders and learned that the Rhodens were dead from TV reports, calling the news “more heartbreaking, more traumatizing than I’ve ever known.”

His younger brother, Edward “Jake” Wagner, earlier testified as part of a deal that spared him the death penalty that he killed five of the eight victims and implicated the brothers’ father in the other three slayings. He said he felt he had no choice but to kill the mother of his toddler daughter because he feared for the girl’s safety.

Angela Wagner, the mother of Jake and George, earlier pleaded guilty to helping plan the slayings but blamed the massacre on her husband, George “Billy” Wagner III. She said he believed the other family would seek revenge for the woman’s death and would kill Jake “if not all of us,” so the rest of her family “had to be murdered.”

George “Billy” Wagner III has pleaded not guilty and likely won’t go on trial until next year. The four members of the Wagner family were not arrested until more than two years after the April 2016 slayings.

Canepa said the Wagners spent three months planning the massacre, buying masks, ammunition and a device to jam phone signals. The two brothers even dyed their hair in the week leading up to the killings, she said.

Those killed were 40-year-old Christopher Rhoden Sr.; his ex-wife, 37-year-old Dana Rhoden; their three children, 20-year-old Clarence “Frankie” Rhoden, 16-year-old Christopher Jr., and 19-year-old Hanna Rhoden, the mother of Jake Wagner’s daughter; Clarence Rhoden’s fiancee, 20-year-old Hannah Gilley; Christopher Rhoden Sr.’s brother, 44-year-old Kenneth Rhoden; and a cousin, 38-year-old Gary Rhoden.