A man accused of dragging a stolen dog to its death in the Colorado National Monument pleaded guilty Thursday in U.S. District Court to a federal charge of aggravated animal cruelty.

Steven Romero, 38, of Grand Junction will remain in federal custody. He is scheduled for sentencing by Judge Philip Brimmer on July 30.

Romero faces up to three years in federal prison, a $100,000 fine or both. Jeff Dorschner, a spokesman for the U.S. attorney's office in Denver, said Romero has not made a plea bargain. Buddy, a German shepherd mix, was found dead Dec. 30. Romero is accused of placing a rope around Buddy's neck, tying him to the back of a truck and driving until the dog died.

Prosecutors say Romero's sister, Melissa Lockhart, had stolen the animal from the back of a pickup in Fruita but later told Romero to "get rid" of it.

Lockhart faces a felony charge of lying to investigators. Separately, she has pleaded not guilty to theft. She is next due in court May 10.

A Facebook page called "Demand Justice for Buddy" has more than 260,000 members, and there were protesters outside the court Thursday.

Denver Post staff and wire reports