The boy was arrested Monday after a tip from the unidentified employer led deputies to check on the family.
Authorities said the boy answered the door and told them his 50-year-old father was dead in the home. The coroner said the man had been dead for about six days. Authorities said they still don't know a motive for the killing.
Before the slaying, the boy was under scrutiny for spraying graffiti, the Eagle County Sheriff's Office said. The father didn't show up for a meeting with deputies last Wednesday to discuss the graffiti investigation in the western Colorado town, but it wasn't until the employer's tip that authorities went to investigate, sheriff's office spokeswoman Jessie Mosher said.
The father's name has not been released, and the juvenile was being held in a detention facility on suspicion of first-degree murder.
The sheriff's office said the boy's mother had not been living in the home with her son or ex-husband, but would not release any more information.
Neighbors told KCNC-TV that the man and his son lived in the home for more than a year, but no one heard anything out of the ordinary until deputies showed up.
Eagle County coroner Kara Bettis said the boy is suspected of firing at least two shots, the station reported.
"There was one to the back of the head and one to the temple," Bettis said. "The one to the temple was contact and the one in the back of his head was from farther away."