The baby sitter told the 6-year-old girl she could play with a forbidden sand castle toy if she didn't tell her parents what he did to her.

The little girl kept the McKinney man's secret for about a year, revealing that she had been sexually assaulted only after she saw the man's photo in his wedding invitation to her family, according to a probable cause affidavit released Tuesday.

The girl's revelations led to the March 23 arrest of Noel Young Anderson, 22, and a public plea for help from police in McKinney, Texas, who say they have found three other child victims. Police fear there could be more.

Noel Young Anderson (Collin County Sheriff's Office)

Police say Anderson has admitted to sexually assaulting four children between the ages of 2 and 6 during the last seven years. Anderson is a member of The Church of Jesus Christ of Latter-Day Saints at 1020 N. Lake Forest Drive in McKinney, where he was a primary instructor for children ages 7 and 8 in 2014. Police say he located his victims through church meetings and came in contact with children through church activities.

Anderson is being held in the Collin County Detention Center on felony charges of aggravated sexual assault of a child and indecency with a child involving sexual contact. Bail is set at $200,000.

McKinney police said Tuesday that no further information is being released at this time.

"Detectives are sorting through the new information they've received to ascertain whether or not there were more victims," spokeswoman Carla Marion Peritz said by email. "The investigation is active and ongoing."

According to the affidavit, the girl's family knew Anderson's family through church. He and his siblings baby-sat for the girl's family.

When Anderson's wedding invitation arrived in the mail on March 7, the girl's father set it on the kitchen table and told the girl and her mother they should go.

"He's bad," the little girl told her parents as soon as she saw Anderson's photo in the invitation. When they asked why, she told them what Anderson had done to her and demonstrated without being prompted, according to the affidavit. She told them about her promise not to tell if Anderson let her play with a sand castle.

Her parents weren't sure at first what toy she was talking about. She pointed to a toy kept high in a closet away from the kids because it creates a mess. The parents inspected the toy and discovered it wasn't in the same condition as when they'd stored it, the affidavit states.

The family filed a report with police the next day. The parents checked old calendar entries and believe the sexual assault occurred when Anderson baby-sat for the family in March 2017, the affidavit states.

The girl later did a forensic interview at the Children's Advocacy Center of Collin County. She gave the interviewer the same details she'd given her parents, describing a sexual assault that she said happened only one time and that "was disgusting," according to the affidavit. She also used drawings to show what happened, the affidavit states.

The girl also told the interviewer the assault occurred in a bedroom with the door locked.

During the forensic interview, the girl said "many times that she was done talking about private things," according to the affidavit.

The girl was unable to remember Anderson's name during the forensic interview but described him as a baby sitter with blond hair. When the interviewer showed the girl the photo on the wedding invitation, she said, "OHHHHHHH I know him. How did you get that? He is the one who did my private thing," the affidavit states.

Police declined to release circumstances involving the other child victims.

Police are asking parents to talk to their children if they may have been under Anderson's care. Anyone suspecting inappropriate contact should reach out to McKinney Police Detective U. Watson at 972-547-2729 or uwatson@mckinneytexas.org.