Authorities are in search of the killer who was behind the “execution-style killing” of eight family members in Ohio. The investigators believe that the Ohio killings were pre-planned and related to drugs as they found three marijuana “grow operations” at rural residences where the slaying took place.

Seven adults and a 16-year-old boy were killed in four different houses at Union Hill Road in Pike County, Ohio, which prompted authorities to believe that they might be searching for more than one shooter. Around 50 to 60 people were interviewed during the investigation.

The victims of the fatal shooting are Hannah Gilley (20), Christopher Rhoden Sr. (40), Christopher Rhoden Jr. (16), Clarence “Frankie” Rhoden (20), Dana Rhoden (37), Gary Rhoden (38), Hanna Rhoden (19), Kenneth Rhoden (44).

People in the county were shaken by the killings and their cold-blooded nature. The victims were all shot in the head while in their sleep at four residences. A mother with a 4-day-old lying beside her was also killed. According to authorities, the newborn, along with a 6-month-old and a three-year-old, have survived.

Attorney General Mike DeWine and Pike County Sheriff Charles Reader have not revealed much about the investigation during a Sunday evening press conference, but said that the investigators found three marijuana grow operations at the scenes of the crime, reported Chillicothe Gazette. Although Reader and DeWine did not confirm whether the shootings were drug related, they said that they were planned and specifically targeted the Rhoden family.

“This was a pre-planned execution of eight individuals,” DeWine said. “It was a sophisticated operation and those who carried it out were trying to do everything they could do to hinder the investigation and their prosecution.”

An official, Nick Valencia, also told CNN, “This operation was not for personal use; it was for something much bigger than that. It was a very sophisticated operation.”

DeWine confirmed that around 50 to 60 people were interviewed and 100 tips were received during the investigation on the Ohio Killings. He also informed that evidence found at the crime scenes would be sent to the state crime lab where they would be analysed along with 18 other related evidence.

Last month, a police dog named Yeti led Northern Territory officials to over 700 ounces of cannabis that was hidden in a man’s car.