Troopers from the Uniontown barracks announced the arrests and arraignments of Patrick Roy Haney and Heather Forsythe, both 27, in the death of Trenton Lewis St. Clair.
Police have charged Haney with criminal homicide and Forsythe with endangering the welfare of a child.
According to police the boy was abused from July until he was taken to Ruby Memorial Hospital, just across the border in Morgantown, W.Va., where he died Tuesday.
The boy's grandmother, Sharon Smitley, said she knew something was wrong in the weeks leading up to his death.
"I called CYS time and time again and I told them there's abuse going on, and I never got a phone call back," said Smitley. "Today, I got one back. It's too late. My baby's dead."
Police said Forsythe told them Haney had been abusing the boy for days and that Haney acknowledged hitting the boy in the face and smacking the back of his head.
According to the criminal complaint, Forsythe told police that Haney "beat her child over the last few weeks. She also told police that Haney "pulled his hair, slapped him in the face and back and left bruises all over him"
The complaint went on to say that Forsythe told investigators that Haney "choked her son and is responsible for his death."
Investigators said Haney was not the child's father.
Brenda Newman, who works at the Riverside Diner in Point Marion, said she saw often saw Trenton with his mother and her boyfriend at the restaurant.
"They just came in to eat several times. I thought he didn't look good because he had black and blue marks all over him. She [the mother] said he had food allergies and that he couldn't eat very much,' Newman said.
Newman said she also noticed that the boy feared his mother's boyfriend.
"Whatever that man said, that little boy did. That's all. What could he do? He's 4 years old. A little innocent baby," said Newman.
The mayor of Point Marion told Channel 11's Courtney Brennan that it was a well-known fact that Children's Services had been called on the couple several times. Carl Ables said he's outraged by the child's death and wants laws to change.
"It's sick. It is sick. Something needs to change in these laws, especially when they've been called out and called out and called out. Sometimes it's time to change something," Ables said.
Investigators said Haney told them that he beat the boy because he wouldn't listen.
Both Forsythe and Haney face court hearings next week.