A teacher who authorities say admitted to fatally stabbing a couple he didn’t know who were hiking with two of their children in an Arkansas state park is expected to have his first court appearance Friday. Arkansas State Police Col. Mike Hagar said authorities are trying to determine a motive for the attack at Devil’s Den, a 2,500-acre (1,000-hectare) state park near West Fork, about 140 miles (220 kilometers) northwest of Little Rock, the state capital. State Police arrested McGann on Wednesday at a barbershop in Springdale, approximately 30 miles (50 kilometers) north of the park, said Maj. Stacie Rhoads, commander of the department’s criminal investigation division.