Steven Romero, 38, was accused of dragging Buddy the dog in the Colorado National Monument. Because it was on federal land, he faced a federal charge of aggravated animal cruelty.
The guilty plea was part of a deal, but Romero will stay in custody until his sentencing on July 30. At the sentencing, he could get up to three years in prison and a $100,000 fine. That was the range of sentencing before the deal was announced, but it was expected he would be offered a reduced sentence.
"It's a good day for animal lovers and I'm happy to see this happen. It was the right thing for him to do to accept responsibility," Assistant U.S. Attorney Michelle Meyer said.
Buddy, a German shepherd mix, was found dead on Dec. 30. Romero is accused of putting a rope around the dog's neck and driving until the dog was dead.
"It needs to not be allowed, it needs to be prosecuted. You abuse an animal you need to go to jail. It's no different than abusing a person," Jennifer Ballard, one of the protestors, said.
Last month, Romero's attorneys filed court documents to let the judge know Romero planned to plead guilty.
Prosecutors say Romero dragged the dog to its death and that his sister, 32-year-old Melissa Lockhart, stole the pup from a pickup truck in Fruita and told him to "get rid" of it.
Lockhart faces a felony charge for lying to investigators. She will appear in court on May 10 in Grand Junction.
A Facebook page was created in the wake of Buddy's death. It is called "Demand Justice for Buddy" and has more than 260,000 members who live all over the world.
(KUSA-TV © 2010 Multimedia Holdings Corporation with The Associated Press)