The agonizing months-long search for 9-year-old Melodee Buzzard has come to a heartbreaking conclusion, as the Santa Barbara County Sheriff’s Office said that her mother, Ashlee, acted alone in the death of her daughter — shooting her child in the head.

The California girl’s body was discovered in Utah in early December, two months after she vanished during an impromptu mother-daughter road trip.

“Maternal filicide is rare and always difficult to comprehend,” Santa Barbara County’s Sheriff-Coroner Bill Brown said on Tuesday.

Brown noted with disgust that the murder was premeditated, ruthless, calculated and heartless, saying that Melodee died from gunshot wounds to the head.

“Melodee was last seen on video surveillance with Ashlee on the Colorado side of the Colorado Utah border on Thursday, October 9,” officials said on Tuesday. “And detectives now believe that Melody was murdered shortly after that stop.”

Her mother was arrested Tuesday for murder and taken into custody without incident, booked for first degree murder where she is being held without bail.

Authorities confirmed that DNA testing was used to positively identify the remains, which were uncovered earlier this month in Utah — an area detectives said the mother and daughter traveled through during a bizarre, multi-state road trip in October.

The chilling saga began in mid October, when the Lompoc Unified School District staff noticed that the homeschooled girl had been absent for a prolonged period of time.

Detectives pieced together a timeline showing the mother and daughter departing on a sudden road trip on October 7. Surveillance footage captured at a Lompoc car rental agency that day showed both mother and daughter appearing to wear wigs — a detail that immediately raised concerns about efforts to evade detection.

During the trip, which routed through California, Nevada, Arizona, Utah, Wyoming, and Nebraska, investigators say the license plate on the rental car was temporarily switched to a New York plate, further fueling suspicions of a cover-up. “She would back her vehicle into gas stations in an apparent attempt to avoid detection by their surveillance cameras,” Brown said.

Detectives searched Buzzard’s home, a storage locker she had rented and the recently rented car, and recovered an expended cartridge case and a live round of “similar ammunition.” An examination of the explosives found at the crime scene in Utah “resulted in a Niben (National Integrated Ballistic Information Network) hit, linking them to the single cartridge case that was found at the Buzzard residence.”

Yesterday, the FBI crime lab notified Santa Barbara authorities that a DNA analysis of the remains found in Utah were a familial match to Buzzard.

Investigators says a motive as to why Ashlee would allegedly do such a horrible thing to her own daughter has not yet been established.

They also say Ashlee has not been cooperative in the investigation since the latest developments.

“While these developments represent important steps towards holding Ashlee Buzzard accountable for the murder of her daughter, they do not diminish the profound loss that we are acknowledging today.”

The case remains active.