Instead, Tyshawn Lee was led off a playground and into an alley, where the child was shot several times at close range in an act of gang war retaliation, prosecutors said.
Those details emerged with the announcement that a second suspect was charged in the November 2015 killing.
Dwright Boone-Doty, 22, was charged with first-degree murder in Tyshawn's death, Chicago police spokesman Anthony Guglielmi told CNN.
John Escalante, acting superintendent of Chicago police, said that even in a city that has witnessed numerous gang-related killings, the slaying of Tyshawn "was something far more sinister."
An act of 'treachery and savageness'
The boy was targeted and killed because his father was a ranking member of a rival gang, Escalante said at a news conference.
"In nearly 30 years of policing, I have never witnessed such a hateful act of treachery and savageness toward an innocent child whose life barely had the chance to flourish," he said.
The second suspect, Boone-Doty, is imprisoned on unrelated criminal charges. A multiagency investigation, including a corrections intelligence team, uncovered evidence to charge the inmate with targeting, luring and executing the boy, Guglielmi said.
Boone-Doty was charged with murder and attempted murder in a separate shooting.
He first planned to kidnap and torture Tyshawn by cutting off his fingers and ears, Cook County State's Attorney Anita Alvarez said.
Alvarez said that Boone-Doty made statements about how he approached Tyshawn at a playground and invited him to a store to buy the boy something.
Witnesses saw the man and the boy walk out of the playground together, Alvarez said. Boone-Doty then led the boy into the alley and shot him several times at close range, Alvarez said.
The other two suspects were with Boone-Doty before the killing, and met with him afterward to purchase cleaning supplies in an attempt to sanitize the vehicle they used that day before abandoning it, Alvarez said.
Third suspect at large
The first suspect, Corey Morgan, 27, was arrested in November and charged with first-degree murder. At the time, police said Morgan didn't act alone, but with two others, including one who was in custody on an unrelated charge. Boone-Doty is the suspect police were referring to.
The third suspect, Kevin Edwards, remains at large, Guglielmi said.
Court papers provided by the prosecutor's office said that "Tyshawn's death is the result of a gang war" between two particular gangs that "came to a boil" after Morgan's brother, Tracy, was shot and killed in a car while with their mother on October 13.
The mother was shot and wounded, court papers said.
"Shortly after the shooting [Corey Morgan] stated that since his brother was killed and his mama was shot he was going to kill grandmas, mamas, kids and all," according to court documents.
An autopsy of Tyshawn's body showed two perforating gunshot wounds, and part of his right thumb was lost as a defensive wound trying to block a gunshot, court papers said. The boy's body had a gunshot wound to the head, a bullet graze wound to his right upper back, and a superficial wound to the right forearm, documents said.
"There was evidence of close-range firing," court papers said.