Special prosecutor Angela Canepa did not accuse George Wagner, 30, of shooting anyone in April 2016, but she said
he took part in planning, carrying out and covering up "one of the most heinous crimes in Ohio history."
He was with his brother and father when they drove to three separate locations where all eight were killed,
went inside with the pair and helped his brother move two of the bodies, Canepa said.
Some of the victims were treated as "collateral damage" by the Wagners, Canepa said.
"They knew that there might be other people there
and agreed they would need to be killed too," she said. "People they had no issue with, they were willing to kill them indiscriminately."
A custody dispute between two families that erupted into the
massacre of eight people in rural southern Ohio started with a plan to kill just one of them, a young mother refusing to give up her daughter, a prosecutor said Monday.
But just months before the
killings in 2016, the family behind the plot decided to kill everyone who could point the finger at them, the prosecutor said during opening statements of the first trial in the slayings.