His body was found around 12:45 p.m. Saturday after searchers drained a septic tank on property near his home in Greene Township, Beaver County, about 25 miles northwest of Pittsburgh, according to Pennsylvania State Police.
"We want to do more tests," Beaver County Coroner Teri Tatalovich-Rossi told the Pittsburgh Post-Gazette, declining to say how long that would take. "The cause and manner will be pending until they're done."
Homicide charges are expected after the autopsy results are completed, but it may take several days, state police said. "It is a homicide investigation," Lt. Thomas Dubovi said. "We believe he (Wyatt) could not have gotten into that septic tank by himself. The cover is too big for a 4-year-old boy."
In reporting him missing, the boy's family told police he was playing outside with two sisters, ages 3 and 6. Hundreds of emergency personnel and volunteers had searched for the boy in dense woods with the help of dogs.
Wyatt had a heart disorder and required medication. After the body was found, the Beaver County Times reported, police questioned the boy's relatives for hours, including his parents, Terri and John Smitsky.
John Smitsky left the police station accompanied by an attorney. The lawyer, Joseph Horowitz of Pittsburgh, said Smitsky maintains he had nothing to do with his son's death.
"As far as he is concerned, it's an accident," Horowitz said. "He's just very upset about the loss of his son, and he wants to go home with his family."