MOUNT CLEMENS — A 37-year-old man who lived secretly in the home of a teenage girl with whom he had a relationship pleaded guilty Wednesday to two counts of criminal sexual conduct.

Wayne Koch admitted to having a sexual relationship with the girl for nearly two years, starting in 2003 when she was 13.

Initially, Koch lived nearby with his mother; last year she moved out of her St. Clair Shores home and forced him to find a place to live.

He first moved into the garage of the girl’s home, without her father’s knowledge. Once the cold weather set in, he moved inside the teenager’s house and would hide under her bed while the teen’s father was home.

"He befriended this little girl and preyed on her youth," said Suzanne Faunce, chief of the Macomb County Prosecutor’s Office sex crimes unit. "He would stay in the house and move around when (the father) was not in the house."

The girl, who is not being named because of her age, eventually told her aunt what was going on after she said Koch threatened her with a gun if she didn’t continue the relationship.

"Fortunately he is not going to put the girl through a trial," Faunce said.

Koch pleaded guilty to two counts of third degree criminal sexual conduct with a person 13-15 years old, assault with a dangerous weapon and felony firearm before Macomb Circuit Judge James Biernat Sr.

He also admitted to brandishing the gun when the girl wanted to end the relationship.

"I threatened her with a gun," Koch said. "I didn’t aim it at her."

Questioned by Biernat about whether he understood the charges, Koch said yes and said that psychiatric medication was helping him. He said he was taking nine prescription pills a day, including the antidepressant Zoloft.

Koch was arrested on Jan. 2 by police following the tip called in by the girl’s aunt.

When police searched the home, they found Koch hiding under the bed with the teen’s father’s Luger handgun.

Faunce said the victim’s father has lost custody. The girl is in foster care.

John Belanger, Koch’s attorney, did not return a call for comment.

Koch will be sentenced June 27, and faces up to 17 years in prison.