Paragould police said in a statement that a juvenile was arrested on a capital murder charge in the death of Nicholas Zurosky. Police would only say Zurosky "appeared to have died from a number of injuries" when they found him at his home on Thursday.
Three other suspects, including another juvenile, were arrested on hindering apprehension charges.
Authorities aren't saying whether Zurosky's death is related to that of Lisa Steele, who was found dead at the same address last week. The relationship between the two teens wasn't immediately clear.
Greene County coroner Dick Pace said Steele was shot and killed on July 6 at the same home where he said Zurosky died.
Arkansas State Police spokesman Bill Sadler said Paragould police contacted his agency on Thursday about a stabbing, but he said the local department was handling the case.
Pace said he couldn't comment on whether Zurosky was stabbed, but he said an autopsy is planned.
Prosecutors and a police spokesman didn't immediately return phone messages for comment.
The two teens were found dead on a quiet block in Paragould, about 150 miles northeast of Little Rock.
Jim McMillon, who lives next door to the home where Zurosky lived, said he saw authorities going in and out of the home on Thursday.
McMillon said the latest death has been particularly hard on Zurosky's father. "He was upset about the girl's shooting, but he's really upset now," McMillon said.
No one answered a phone number at the home on Friday, but a cheery answering machine message still mentioned Zurosky's first name.
"To me, it's senseless," McMillon said. "Two 18-year-olds are gone and they had a long life probably ahead of them, or should have."