Marijuana "grow operations" were found at three of the four shooting sites, according to the attorney general

The shooting of eight people in rural Piketon, Ohio, was “a pre-planned execution,” Attorney General Mike DeWine said during a press conference Sunday, according to the Associated Press.

The victims – seven adults and one teenage boy from the same family – were shot at four separate homes, the attorney general said, calling the slayings “a sophisticated operation.”

No suspect has been arrested in the execution-style shootings, but Pike County Sheriff Charles Reader said more than 30 people have been interviewed in pursuit of leads, according to the AP.

“We will be with this investigation, and with the sheriff until we find out who did this,” DeWine promised.

Two of the homes were in walking distance of each other off of a rural highway, while the third house was over a mile away, and the fourth located on a different road, according to the AP. DeWine also noted that marijuana “grow operations” were found at three of the locations.

Ahead of Sunday’s press conference, the Attorney General’s Office released the names of the victims: Christopher Rhoden Sr., 40, Christopher Rhoden Jr., 16, Kenneth Rhoden, 44, Gary Rhoden, 38, Dana Rhoden, 37, Clarence Rhoden, 20, Hannah Gilley, 20, and Hanna Rhoden, 19. Some small children present at the sites were not injured, according to the AP.

Authorities are offering a $25,000 reward – provided by a Cincinnati businessman – for any information that leads to the arrest and conviction of the killer or killers, the attorney general announced on Saturday. Anyone with information is urged to call 855-BCI-OHIO or the Pike County Sheriff at 740-947-2111.