The woman told officers her 10-year-old daughter was still in apartment 808, from which they had escaped.
With the fire alarm blaring, they busted in the front door and searched the smoke-filled apartment for Victoria Martens.
In the bathroom, the real crime began to come into focus.
Investigators took into custody the mother, her boyfriend, and his cousin.
The community was left struggling to understand how a child who loved swimming and gymnastics could have been the target of such violence on the day of her 10th birthday.
Police said Victoria was injected with methamphetamine, sexually assaulted, strangled, and stabbed before being dismembered.
“This homicide is the most gruesome act of evil I have ever seen in my career,” said Albuquerque police chief Gorden Eden Jr.
The girl’s mother, 35-year-old Michelle Martens, her 31-year-old boyfriend, Fabian Gonzales, and his 31-year-old cousin, Jessica Kelley, face charges of child abuse resulting in death, kidnapping, and tampering with evidence.
Mr Gonzales and Ms Kelley also face charges of criminal sexual penetration of a minor.
Bail was set at $1m each for Ms Martens and Mr Gonzales at their first court appearance.
As news spread about Victoria’s death, neighbours and friends built a makeshift memorial under a tree near the apartment complex, adorning it with stuffed animals and candles.
In the evening, dozens gathered for a candlelight vigil and the shrine grew.
Mugshots of Ms Martens and Mr Gonzales released by police showed them with bruises on their faces.
According to the complaint, Mr Gonzales said his cousin hit him and Ms Martens with an iron, prompting him to jump over the balcony. Ms Martens also escaped.
Ms Martens told police she met Ms Gonzales online about a month ago and he drugged the girl so he could calm her down and have sex with her, the complaint said.
Mr Gonzales has a New Mexico arrest record stretching back to 2004, including a felony child abuse charge, driving while intoxicated, and resisting arrest. He pleaded no contest to a charge of child abandonment in 2015.
Ms Kelley’s record includes battery, domestic violence, and drug charges.