A Fairfax County police spokesman, a 15-year member of the force, has been charged with possessing child pornography that was uploaded to the Internet from a computer at his home, police said.

Officer William “Bud” Walker, 49, of Fairfax was arrested at police headquarters Wednesday afternoon and charged with two counts of possession of child pornography following an investigation, police said.

Fairfax County Police Chief Edwin C. Roessler Jr. said at a press conference Wednesday night that it "gravely upsets" him to inform the public about Walker's arrest.

"At this time, this criminal investigation has not revealed any activity involving children from our community," Roessler said. He added that the children seen in the pornography have not been identified.

Walker was regularly seen on television and was quoted in the newspaper, providing information about police cases in the county. Police said in a news release that Walker held a “visible position of public trust.”

Booking photo of Officer William “Bud” Walker (Courtesy of Fairfax County police)

County detectives began their investigation April 6 after being contacted by the National Center for Missing and Exploited Children.

In July 2014, the center received a tip from a blogging site, Tumblr, that child pornography had been uploaded through its servers, according to a search warrant. Between April and June 2014, Tumblr reported, one image and one GIF — a looped video clip — were uploaded from an Internet address in the county. The images showed pubescent males.

On April 8, detectives determined that the material had been uploaded from Walker’s home, and Walker was relieved of duty the next day, police said. A police spokeswoman said she did not know whether Walker had created the pornography.

Walker was hired by the county police in 1999. He worked patrol and did a stint as a spokesman before becoming a school resource officer at South County High School from November 2006 until August 2009. He served as a department spokesman again from 2009 until his arrest.

Walker was being held without bond at the county jail. Police said additional charges are possible as the investigation progresses. Detectives urge anyone with information about the case to call 703-246-7896.

This story has been updated.