The teen waived his right to appear in court on Friday.
Senior Deputy Prosecuting Attorney Michael Mohandeson said the 14-year-old boy lured the 8-year-old victim into the woods near the Red Lion hotel in Kent and then physically and sexually assaulted her.
"He went to the place where the victim was and under false pretenses asked her to come outside to show her a surprise," said Mohandeson.
The victim suffered a concussion and may have lost consciousness. According to arrest records, the suspect is 5'10" tall and weighs 230 pounds. Police said the teen hit the young girl twice in the face when she said she was going to call police.
The teen later claimed what happened was consensual, according to the probable cause statement.
When the girl walked into the Red Lion hotel for help she was wearing only a shirt and socks, according to court documents.
"She did walk into the lobby and advised the reception area of what occurred," said Kent Police Det. Melanie Frazier.
Police arrested the teen at a home in the 600 block of 5th Avenue South, just a few blocks from the hotel.
People who live at the home said the 14-year-old suspect began staying there after his mother died.
They also said when the teen arrived at the home on Thursday afternoon he was breathing hard and was sweaty. He was not wearing shoes or socks and his pants were below his knees. He told them that three guys attacked him.
The 8-year-old victim was treated at a hospital and later released. She told police she'd seen the suspect around the neighborhood but didn't know him.
Police said the teen is a friend of the victim's family.