(CNN) -- In the final weeks of his brief life, little Myls Dobson suffered unspeakable acts of neglect and violence.
A New York criminal complaint released Friday at the arraignment of Kryzie King, 27, with whom the 4-year-old had been staying since mid-December, said the boy had burn marks and abrasions on his head, neck, face and testicles. There were bruises and numerous marks made by an object on his abdomen and legs and wrists -- bruises consistent with being restrained -- lacerations to his fingers, abrasions to his armpit, and bruises and scars on his back. The child appeared malnourished, the complaint said.
Myls suffered "horrific injuries sustained over a period of days," New York Police Commissioner William Bratton told reporters.
King pleaded not guilty at her arraignment in Manhattan criminal court on charges of first-degree assault, first-degree reckless endangerment, endangering the welfare of a child and unlawful imprisonment. But Assistant District Attorney Nicole Blumberg told the court Friday that King also was being investigated on suspicion of murder, and likely faced additional charges upon the completion of the autopsy.
In a statement, King's attorney, Bryan Konoski, said: "My client is not charged with homicide at this time and she is presumed to be innocent of allegations against her. I would tell everyone not jump to any conclusions at this time."
Shortly before 11 a.m. on Wednesday, police responding to a 911 call found Myles locked in a bathroom at King's apartment at The Ritz Plaza, a luxury highrise in the Hell's Kitchen section of Manhattan. He appeared battered, was unconscious and unresponsive on the floor, authorities said.
The child was pronounced dead at St. Luke's Hospital at 1:52 p.m.
King told police that Myls' father dropped the child off for her to watch on December 17 and that she was the "child's primary and sole caretaker" until the time of his death, the complaint said. The father was arrested in December for alleged bank fraud, according to CNN affiliate WCBS.
At a news conference Friday, an adviser to the boy's mother, Ashlee Dobson, said that she lost custody of her son for financial reasons. The mother and the adviser, Tony Herbert, demanded answers from child welfare authorities.
"The city of New York put the child in the care of the father, who they knew was a felon," Herbert said. "You open up a case and then you close it thinking everything is fine? No. That has to be answered. Who did that, who authorized that?"
A call placed to the city Administration for Children's Services was not returned.
Dobson lost custody in 2012, according to CNN affiliate WCBS.
"She was in a shelter, they didn't think it best that she would be in that shelter with a baby, so they gave him to the father," Herbert said of child welfare authorities.
Dobson told reporters Friday that she was turning her life around in hopes of regaining custody of her son. She had weekly visitation rights but last saw her son in November.
In tears, Ashlee Dobson said, "I love my son. He always loved me. He always gave me kisses."
The complaint portrays the finals weeks of Myls' life as a living hell.
King told police that on December 29 she removed a hot rack from an oven with a glove and allegedly placed it against the boy's right leg, leaving linear burn marks, the complaint said. The next day, she told police, she allegedly struck him about his body five to six times with a belt, leaving bruises and scars.
The complaint said King admitted that from December 30 to January 4 she allegedly tied the boy's wrists and feet together with shoe laces and gagged him with a piece of cloth. She told police that resulted in scaring on his wrists and ankles. On the day she freed him, the complaint said, King allegedly beat him twelve to thirteen times with a belt.
On Tuesday, during subfreezing temperatures, King told police she allegedly locked the the child, wearing only a T-shirt and shorts, outside on a balcony from 20 minutes to an hour, the complaint said. That same day, she allegedly locked the boy inside a dark bathroom for about three hours.
King told authorities that the boy was "being very difficult eating and that the last full meal he ate was on December 26, 2013; after that he would only pick at his food," the complaint said. The last time the boy ate or drank anything was on January 3.
Aside from her comments about the child not eating well, King gave no indication in the complaint of what might have prompted her purported actions.
Since arriving at King's home on December 17, the complaint said, Myls Dobson lost 20 to 25 pounds.
Julie Bolcer, a spokeswoman for the city medical examiner's office, said an autopsy was performed Thursday but the cause of death is pending further study.
CNN's Julia Talanova contributed to this report.