Story highlights The boy's brother and the brother's wife allegedly abused the boy

They are charged with kidnapping, unlawful imprisonment and assault

The boy is from Atlanta and was staying with them for the summer

He escaped two weeks ago by chewing duct tape off his hands

A Seattle-area couple is in custody for allegedly holding captive and torturing the man's 13-year-old brother for three months -- including driving a nail through the boy's hand and keeping him in a cellar for days without food, the prosecutor said Wednesday.

Brandon Gunn, 27, and his wife Viviana, 34, are in the Kitsap County Jail outside Seattle on $500,000 bail each, charged with kidnapping, unlawful imprisonment and four counts of assault, county prosecutor Cami Lewis said.

Brandon's brother is from Atlanta and went in May to stay with his brother for the summer, Kitsap County Deputy Sheriff Scott Wilson said.

"We've been crying for days," the teen's aunt, Marsha Thomas-Jones, told CNN Atlanta affiliate WSB . "My sister is devastated."

The alleged torture began as early as May 1 and lasted until the teenager escaped from his brother's cellar two weeks ago, according to the prosecutor's complaint, filed Tuesday.

Thomas-Jones said the family suspected something was wrong months ago when communication ceased, and it tried unsuccessfully to get law enforcement involved early, WSB reported.

The attorney for Brandon Gunn, Michele Taylor, was given the case only Wednesday and has not received any discovery documents, said her paralegal, Samantha Badkin. She said they don't expect to speak to their client until at least next Tuesday.

A voicemail message for Viviana Gunn's attorney, Jeniece Lacross, was not returned late Wednesday.

According to the probable cause certificate filed Monday by the Kitsap County Sheriff's Office, the boy was sent to the Gunns' garage where he was duct-taped to a chair with tape over his eyes and mouth, then beaten in the head, torso and legs with a baseball bat and metal bars, losing consciousness at times.

Another time, the couple put the boy's hand in a bench vise, tightened it, and drove a nail through the his hand with a hammer, the certificate says. The boy said that time, he could see them doing it.

The Gunns duct-taped his hands and hung him from a rafter in the garage, then beat him; they also stapled his right palm with a construction stapler, heated a knife and cut him with it, according to the certificate.

The couple forced the boy to stay naked in a portable dog kennel twice for two to three days at a time, with no food or water, the certificate says. He also was forced to stay in the dark cellar for four days, and when he escaped to get food, he was punished by being beaten with a baseball bat, it says.

The boy said the couple called the abuse "punishment sessions" for not doing chores or breaking household rules, and that the "sessions" would last for two to three hours, according to Deputy Sheriff Wilson.

When the boy escaped, he had been duct-taped but managed to escape by moving his hands in front of him, peeling the tape off his mouth, then chewing through the tape binding his hands, Wilson said. He forced open the cellar door and then lived on the streets for two weeks, stealing food when he could, Wilson said.

He was sleeping in a bus shelter on a Navy housing complex last Friday night when two Navy security officers found the boy and saw his injuries, Wilson said. They immediately sent the boy to a hospital where detectives interviewed him.

They saw injuries to the boy's head, face, chest, abdomen, back, arms, legs, hands and feet, ranging from fresh open wounds to wounds that were in the process of healing, the certificate of probable cause says.

The doctor also found a broken piece of metal in the boy's hand, possibly from the nail.

"In the first six hours they were able to develop enough probable cause for the arrest of the brother and the brother's wife," Wilson said. "they were arrested at 7 a.m. (Saturday) at their house."

When detectives interviewed Brandon Gunn, he denied abusing the boy, saying only that he gave him a "whooping" with a belt on his backside a few times.

Detectives searched the home and found blood stains on the wall, door, bench vise, baseball bat and chair, the certificate of probable cause says. They also found the dog kennel and staple gun, and a strong smell of urine in a corner of the cellar where the boy said he was forced to urinate, it says.

The boy is out of the hospital and living with a foster family, Wilson said.

The Gunns' next court appearance is scheduled for September 10 in Kitsap County District Court, said Lewis, the prosecutor.