CHICAGO — The trial of two men charged with first-degree murder in the 2015 slaying of a 9-year-old Chicago boy got underway Tuesday with a prosecutor noting the victim brought a basketball to a park while his alleged killers "brought guns."

Dwright Boone-Doty and Corey Morgan are charged with first-degree murder in the slaying of Tyshawn Lee.

Boone-Doty and Morgan are being tried together but before separate juries, each of which will only consider the evidence as it pertains to one of the two.

Assistant State's Attorney Margaret Hillmann on Tuesday said Boone-Doty lured the fourth grader into an alley by promising him a juice box and then shot him. She asserted the defendants killed the boy because they believed his father was a member of a rival gang responsible for the shooting death of Morgan's brother and the wounding of their mother.

Hillmann noted Tyshawn hadn't bothered to change out of his school uniform before heading to a park to play basketball.

"Tyshawn brought a basketball to Dawes Park. Corey Morgan, Dwright Doty and Kevin Edwards brought guns," said Assistant State's Attorney Margaret Hillmann, naming the two defendants and a third man who pleaded guilty before trial.

Morgan's attorney, Thomas Breen, tried to distance his client from the crime.

"That execution of that 9-year-old boy has to come from one singularly evil person," Breen told jurors without naming Doty. "Not from a plan. His killer did so of his own volition and for his own reason. Not at the behest or help of Corey Morgan."

Hillman said DNA linked to Boone-Doty was on the basketball that was found next to Tyshawn's body. She added prosecution witnesses identified the two men as being in the park with the victim before the shooting.

Prosecutors allege Boone-Doty was the gunman. His attorney, Brett Gallagher, encouraged the jury to view the prosecution case with skepticism.

Hillmann said Boone-Doty befriended Tyshawn to gain his trust after the boy arrived at the park. Boone-Doty picked up the boy's basketball and lured him to a nearby alley as Morgan and Edwards watched from a black SUV, she said.

"And Dwright Doty took out a .40-caliber handgun, and he executed Tyshawn in broad daylight," she told jurors.

The third man accused in the attack, the alleged getaway driver Edwards, pleaded guilty to first-degree murder in exchange for a 25-year prison sentence.