Search crews near Gastonia, North Carolina, discovered a body Thursday, believed to be that of Maddox Ritch, an autistic and nonverbal 6-year-old missing since last Saturday.
Authorities say the body was found in a creek, about a mile east of Rankin Lake Park, where his father had last seen him.
Gastonia Police Chief Robert Helton told reporters, "This is not the end that we had hoped for."
Authorities said the water where the body was found was about 2-3 feet deep, but there are various depths in the creek. The body was partially submerged.
FBI officials said it is too early to determine if foul play was a factor.
According to Ian Ritch, the boy's father, Maddox was some 30 feet away from him in the park when the youngster sprinted away. "I couldn't catch up with him," the father said. "I feel guilty for letting him get so far ahead of me before I started running after him."
The medical examiner's office has yet to formally identify the body.