UTICA, N.Y. (WKTV) - A Town of Lee man will spend the next 18 years to life in prison for video taping himself sexually abusing an autistic girl, possibly as young as age eight.

Brett Salmon was sentenced Tuesday after previously pleading guilty to Predatory Sexual Assault Against a Child.

Salmon admitted in court to sexually assaulting an autistic girl who lived in his neighborhood and video taping it.

Oneida County Assistant District Attorney Dawn Lupi said the victim is currently 13 years old. However, because of her mental state, it is unclear when the sexual assault started.

The girl believes she can remember it happening around age eight, Lupi said, adding that the assault went on for several years.

"I think sexually abusing a child, obviously, is a horrible crime, but when you take advantage and sexually abuse a child who has some mental limitations, then video tape it, it is just really horrifying," Lupi said. "It really is."

In court on Tuesday, Lupi, read a letter that the victim's grandfather wrote on her behalf. The letter stated the victim's family helped Salmon out when he was in time of need and took care of them.

The letter went on to say: "We don't understand why this happened, we thought we could trust you. I don't understand the evil inside you, I never will. You lost you friends, family and rights."