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A 10-year-old girl was drugged, sexually assaulted and killed Wednesday in what the Albuquerque Police Department called one of the worst cases in the department’s history.

Michelle Martens is seen after she was arrested following her daughter's killing on Aug. 24, 2016. (Credit: KOAT)
Michelle Martens is seen after she was arrested following her daughter’s killing on Aug. 24, 2016. (Credit: KOAT)

Police have arrested three people in the case: Michelle Martens, 35, the victim’s mother; 31-year-old Fabian Gonzales, the mother’s boyfriend; and his cousin, 31-year-old Jessica Kelley.

Martens and Gonzales allegedly confessed to injecting the 10-year-old daughter with meth “to make her calm down so they could do what they wanted with the little girl,” police said, according to Albuquerque television station KOAT.

The child was allegedly sexually assaulted by Gonzales and Kelley before she was stabbed and strangled, KOAT reported.

Her mutilated body was found wrapped in a blanket at an apartment complex. The girl was identified by KOAT as Victoria Martens.

“What happened to this little girl is … horrific. It’s one of the worst things I’ve read in my entire life,” police spokesman Tanner Tixier said at a Wednesday night briefing on the case.

Martens appeared not to show any remorse with police detectives, according to Tixier.

The girl turned 10 the day before she was killed, and her friends told KOAT they had planned to celebrate her birthday.

“I can’t speak to what this mother was planning for her child other than the horrific events that happened to this child,” Tixier said. “I would find it hard to believe that she was planning a birthday party for this child.”

Kelley has refused to speak to investigators thus far, the station reported. Court records obtained by KOAT showed she had a lengthy criminal record that included battery, DWI, assaulting a police officer and shoplifting.

Gonzales and Kelley face several charges, including criminal sexual penetration of a minor and child abuse resulting in great bodily harm or death, according to the TV station. Gonzales also faces a charge of kidnapping, as does Martens.

“This is a horrific tragedy for our community,” Albuquerque Police Chief Gordon Eden said at a news conference on Wednesday. “When something like this happens to our community, it has an effect on each and every one of us.”

CNN contributed to this story.