This sounds, to put it mildly, very suspect.
Details are in the statement from the Archdiocese of Galveston-Houston:
Yesterday, a number of Chancery Departments, along with at least one Pastor, began receiving copies of a letter addressed to Bishop George Sheltz from an individual identifying herself as Yannah Nowak. Her letters do not have a return address or any contact information and our efforts to identify any individual by that name have been unsuccessful.
In the letter, the author makes an accusation that she was molested by Bishop Sheltz in 1971, when she was a minor. The author also expressed anger and outrage over the recently announced decision of the Archdiocese to move her Pastor, Father Hai Dang, to another parish assignment. The author closes the letter with a threat to Bishop Sheltz that if he goes forward with Father Dang’s new assignment, she will go public with her accusation against Bishop Sheltz.
Bishop Sheltz has served as a priest of this Archdiocese for more than 48 years and has never had a single complaint of inappropriate conduct with minors or adults. We firmly believe this allegation to be completely false. It seeks to use blackmail tactics to keep a Pastor in his current assignment while casting a shadow on what we know is a lifetime of superb and selfless priestly ministry.
While we firmly believe this accusation lacks any credibility, we have reported it to the Houston Police Department and Children’s Protective Services for investigation. Since the allegation has been made against a bishop, we have also notified the Apostolic Nuncio to the United States.
Bishop Sheltz will continue his valued assistance in the Chancery Office, but he has volunteered to temporarily step aside from public priestly ministry.
If you become aware of any related information or any other allegation of abuse of a minor, we urge you to notify civil authorities immediately (local law enforcement and CPS).
Please keep Bishop Sheltz and all those impacted by abuse in your prayers.