Sheriff’s detectives and county prosecutors are looking for other victims – perhaps many – of a Seattle man who has been charged with cyberstalking with sexual motivation.

They want the victims to come forward to tell their stories.

William Thomas Pritchard, 23, who gave his last address as the University District in Seattle, has been charged by the King County Prosecutor’s Office. He is in custody and additional charges are expected to be filed, according to the King County Sheriff’s Office.

The sheriff’s investigation led to a recommendation to the Prosecutor’s Office of 269 counts of cyberstalking, communicating with a minor for immoral purposes, harassment and extortion.

The 269 is the number of calls Pritchard made to a then-17-year-old girl between Dec. 27, 2009, and March 23, 2010. Her name wasn’t revealed in charging papers; she was a student at Skykomish High School. She’s now 18.

Detectives believe Pritchard cultivated a relationship with the girl on MySpace. Pritchard eventually began demanding nude photos of the girl via e-mail, and made explicit threats to the girl and her family if the photos were not sent.

The girl received approximately 30 nude photos of Pritchard, along with sexually explicit comments.

Pritchard was able to get the girl’s hometown and cell-phone number from her MySpace page and left threatening messages on her voice mail and when she answered the phone. These threats went on for several months until the Sheriff’s Office became involved.

According to charging papers, Pritchard said he would get his friends to kill her and her family; that he would kill her and carve his name into her chest; and that if she called the police he would kill her.

Pritchard has 2008 felony convictions for cyberstalking. He also has arrest warrants outstanding for cyberstalking and harassment from Seattle and Pierce County, respectively. He apparently lived in Auburn at one time.

Based on a review of cell phone records received in obtaining a search warrant in the case, sheriff’s detectives believe there may other victims living in Pierce, Thurston, Snohomish, and King counties.

If anyone has been getting harassing or obscene phone calls from William Pritchard, they are asked to call the King County Sheriff’s Office at 206- 296-3311 (24 hours) or their local police department.