Ohio Attorney General Mike DeWine said there will be "ample security" at the funeral for six of the eight people shot and killed in what authorities are calling a planned attack targeting one family.
Tuesday's service at a West Portsmouth church is the last of three funerals for the victims.
Seven adults and a 16-year-old boy from the Rhoden family were found dead April 22 at four properties near Piketon, about 80 miles east of Cincinnati. Authorities say all eight were shot in the head, and some had other gunshot wounds and bruising. Three young children were unharmed.
Authorities haven't determined who killed them or why.
DeWine said investigators have conducted nearly 130 interviews and are reviewing about 450 tips and more than 100 pieces of evidence.