Update: This article has been revised to include a response from the Vatican that was received after the article’s initial publication.

The Vatican’s former ambassador to the United States quashed an independent investigation in 2014 into sexual and possible criminal misconduct by Archbishop John C. Nienstedt of St. Paul and Minneapolis and ordered church officials to destroy a letter they wrote to him protesting the decision, according to a memo made public on Wednesday.

The detailed memo was written by an outraged priest, the Rev. Dan Griffith, who was working in the top ranks of the archdiocese and was the liaison to the lawyers conducting the inquiry. He wrote that the ambassador’s order to call off the investigation and destroy evidence amounted to “a good old fashioned cover-up to preserve power and avoid scandal.”

The document offers a grave indictment of the conduct of the Vatican’s ambassador, and will probably put pressure on Pope Francis to discipline him and Archbishop Nienstedt. The former ambassador, Archbishop Carlo Maria Viganò, served as Pope Francis’ representative to the church until he retired in April.