A Washington father walked in on a day care worker sexually assaulting his 5-year-old daughter, police said.

Ian William Moore, 30, was arrested Friday after a man went to pick up his daughter at Kid's Country Day Care in Normandy Park, where he found Moore and the girl "crouched behind a bookshelf," KOMO News reported.

Moore reportedly told the man they were having a "tickle fight," but the girl later told her father that Moore had touched her inappropriately beneath her underwear, police said.

The father told the day care center about the June 5 incident and the facility reported the allegations to Child Protective Services.

During police interviews, Moore reportedly said he touched the girl accidentally.

He was charged with first-degree child rape and is being held at King County Jail on $200,000 bail.

Kid's Country Day spokesman Justin Montermini said Moore was placed on leave and had passed background checks.