Poole "brutally beat him in front of three of her own children," Hennepin County Attorney Mike Freeman told reporters. He said she lied to police, telling them the boy had been abducted.
According to the criminal complaint, Poole's 6-year-old son told police Poole had told him and her 4-year-old child to hold Demond down by the arms while she beat him.
"The death of Demond is tragic in itself. Having that death and beating observed by a 4-year-old, a 6-year-old and an 11-year-old just compounds the tragedy," Freeman said.
Prosecutors were looking into whether there was enough evidence of premeditation to ask a grand jury for a first-degree murder indictment. She was being held on $1 million bail.
The criminal complaint said Demond had injuries inside his mouth that were consistent with a blunt object being shoved in it; rib fractures; puncture wounds on his stomach; a bite mark on his stomach; and bleeding inside his brain.
Poole could not be reached for comment as prisoners at the county jail are not allowed to take calls. Freeman said he expected she would be assigned a public defender at her first court appearance Wednesday.
Poole's four children were placed in a children's shelter and the county is seeking to terminate her parental rights and notify the children's fathers, Freeman said.
He said there was no evidence Poole had ever seriously abused her children before they witnessed the fatal beating.
Demond, who was from Chicago, came to Minneapolis around Christmas with his father, Tony Reed, who left Demond with Poole, his cousin, after he was arrested Jan. 22 on an unrelated matter.
He was still in the county workhouse the weekend of Feb. 1, when the complaint alleges Demond was beaten.
Poole told her 11-year-old daughter last Wednesday to call Demond's relatives and say he was missing, the complaint alleges. Poole told police that a friend named Shawna had taken the boy without her knowledge or consent -- a story authorities say was a lie.
According to the complaint, the 11-year-old told police on Saturday that her mother had "spanked" Demond after he soiled his pants, and that Demond had a seizure and began vomiting. She said his health deteriorated over the next several hours, and that Poole discussed calling 911 but decided not to because she was afraid.
Demond then stopped breathing, and Poole's efforts to revive him with CPR failed, the girl told police, according to the complaint. She said Poole put a blanket over the boy and left him on a bed for about two days before stashing him in a closet.
Police then got a search warrant and brought in a cadaver-sniffing dog for a second time, and found Demond's body early Sunday. Poole's fingerprints were on the plastic bag, the complaint said.
A homicide investigator interviewed Poole after advising her of her rights, and she eventually confessed to killing the boy, according to the complaint.
