CASTLE ROCK, Colo. -- Castle Rock police are investigating a case of possible child abuse involving a foster child who was taken from his birth parents a month ago.

Timothy Dodge's father blames the foster parents for the abuse and the Adams County social services for letting it happen.

Timothy (pictured, left) was airlifted to Children's Hospital on Monday with some kind of brain injury. He remains there in critical condition. Timothy's grandmother told 7NEWS that he has undergone surgery, and is now on a ventilator.

Timothy Dodge Sr. said it was a relative who told him that his son had been rushed to the hospital.

"They had to flight for life my son in. I didn't know what to think. I mean, serious head trauma. He's only 2 1/2," Dodge (pictured, left) said. "Right now, I'm just praying to God he doesn't die."

In early January, Adams County social services took Timothy and his sister from Dodge and his wife after a court found them unfit to be parents, a decision the Dodges strongly opposed.

The children were put in a foster home in Castle Rock, where Dodge claims they were mistreated. He went back to social services to plead his case.

"I asked them to remove those kids from that place. I said, 'Look, they're being abused. Look, I mean, I'm showing you, there's bruises, there's marks, there's scrapes, there's cuts,'" Dodge said.

He said his wife, who visited their children several times, had the pictures to prove what they were telling social services was true -- that the kids were being hurt by their foster parents. But the children still weren't removed until the boy was taken away in an ambulance on Monday.

A spokesman for the Colorado Department of Human Services said, "We are terribly concerned when there's an allegation of abuse on the part of a foster parent. Kids in foster care are our responsibility and we carry a higher burden."

The boy's father has serious doubts about that statement.

"They're supposed to be protecting these kids. How can you protect them if you're not even really looking out for the best interests?" Dodge asked.

Timothy's sister has been removed from that home. Neither Castle Rock police nor social services are commenting specifically on this case.