Authorities are searching for 8-year-old Devin Holston.
A fourth victim was found in a residence about 1/4 mile north on state Route 93, at a relative's residence. This victim was suffering from apparent stab wounds to the neck and head and was flown by helicopter to Cabell Huntington Hospital.
The following counties are included in the endangered missing child advisory: Brown, Butler, Clermont, Clinton, Hamilton, Highland, Warren, Adams, Jackson, Lawrence, Pike, Ross, Scioto, Vinton, Athens, Gallia, Meigs, Morgan and Washington.
The sheriff's office said earlier Thursday there was reason to believe Holston was injured or in danger. The National Center for Missing and Exploited Children has been contacted and is assisting the LCSO in the search for this child.
Authorities say Aaron Lawson, 23, 15868 State Route 93, is a person of interest in the crimes.
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The Lawrence County Sheriff's Office said deputies were called to an Elizabeth Township trailer around 7:30 p.m. Wednesday where three adults were found dead. The sheriff's office said all three people had gunshot wounds.
Anyone with information about Lawson's or Holston's whereabouts should contact the Lawrence County Sheriff's Office at 740-532-3525.
He is described as a white, 7-year-old child, weighing approximately 80 pounds and is 4 feet 8 inches tall.
Victims' names are not being released at this time pending identification and notification of family.