A teenager was charged on Tuesday with killing and raping his sister and beating his niece with a sledgehammer in a crime the sheriff called one of the most brutal he's ever seen.

Walter Smith Jr., 16, was charged with the first-degree murder and rape of his 22-year-old sister, Betsy Mary Smith, and aggravated assault against his two year-old niece, Andrea Costello.

Smith was charged after he recounted Monday morning's events to Spotsylvania detectives, said Sheriff Howard Smith. Based on Walter Smith's accounts, police said Betsy Smith was beaten with a sledgehammer and stabbed before being raped. When Costello began crying, she was struck in the head with a sledgehammer. Betsy Smith, Costello and a 1-year-old boy were then locked inside the room.

"This is probably one of the more brutal cases that I've been involved in here," said Sheriff Smith, who has been with the sheriff's office for 22 years.

Walter Smith will likely be tried as an adult, said Spotsylvania County Commonwealth's Attorney Bill Neely.

Sheriff Smith said a detective went to the house Monday night after a hospital worker called to report a suspected case of child abuse after Costello was brought in for treatment. The toddler was later flown to a hospital in Richmond and listed in serious but stable condition with a fractured skull and nose.

A detective found family members of the child, including Walter Smith, in the house, the sheriff said. The detective found the dead body of Betsy Smith inside the padlocked room.

The sheriff said the children were not found until one of them began crying on Monday afternoon and Betsy and Walter Smith's mother, Mary Smith, told Walter to go check on them.

"Her face was messed up," Mary Smith said of Costello, who was the child of another one of Mary Smith's daughters. "I asked Andrea after I cleaned her face up what happened to her. She said she fell and bumped her head against the fuse box."

Mary Smith said she does not believe Walter Smith killed his sister.

"He don't remember nothing he did," she said. "He was out of it or something like that. It was an accident. He don't remember that stuff."

Mary Smith said her son had no history of violence, but said he was on medication for depression.