A retired priest from the Diocese of Madison in Wisconsin, was charged with six counts of second-degree sexual assault of a child after an altar boy who served with him told police he was abused by the cleric at least 100 times between 2006 and 2010.

Fort Atkinson Police Chief Adrian Bump announced the arrest of Father William Nolan, 64, during a press conference on Thursday.

The accuser, who is now 25, came forward in April, and said the abuse took place at St. Joseph’s Catholic Church in Fort Atkinson when he was 13.

He said the abuse took place in the church office, Nolan’s residence, the altar boy room at the church, at a park, and on a ski trip.

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Nolan retired from full-time ministry in the diocese in 2007, at his request. The diocese said his last assignment was as pastor of St. Joseph Parish, where the alleged abuse took place.

He was reported to be in residence at Our Lady Queen of Peace in Madison at the time of his arrest.

The diocese also said Nolan was being put on administrative leave, which “includes a total exclusion from any exercise of priestly ministry while the matter is pending.”

Bump said more charges could be filed against the priest.

“This is a delay report of almost 13 years. Based off our interaction and working closely with the victim it was identified that a concern that there may be other kids out there that were assaulted and that resulted in motivating the complainant to come forward,” the police chief said.

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The Diocese of Madison began its own canonical process of investigating these allegations, and the diocesan Sexual Abuse Review Board was also engaged in the case.

The diocesan statement said the accusations against Nolan were made directly to the civil authorities in Fort Atkinson, and the diocese was only informed after the priest’s arrest was set in motion.

“We will cooperate fully with those investigating the allegations and desire to allow the legal process to run its course. We appeal to all to cooperate and respect the legal proceedings and for prayers for all affected by these very serious charges,” the statement said.

Nolan appeared in court on Thursday through a video-link, and was freed on a $50,000 signature bond. The priest was told he could not leave Wisconsin, could not have contact with any children, and could not contact the alleged victim.

A preliminary hearing in the case will be held on June 5.