Opening statements in the trial of two men charged with murdering 9-year-old Tyshawn Lee are set to begin Tuesday morning.

Tyshawn’s 2015 murder, described by Cook County prosecutors as a targeted execution of the fourth grader, shocked the conscience of a city that saw some 450 killings that year.

Dwright Boone-Doty, the alleged gunman, is accused of luring Tyshawn from a Dawes Park basketball court with the promise of candy, only to shoot the boy multiple times at close range, leaving him to die in an alley.

The motive for the killing, prosecutors said, was revenge for the murder of the brother of Boone-Doty’s co-defendant, Corey Morgan. Tracey Morgan was gunned down three weeks earlier in an attack that had also injured the Morgan’s mother.

The wounding of the Morgan’s mother was a breach of an unwritten code of gang violence that children and non-gang family members of the combatants are not to be intentionally targeted, prosecutors said. Corey Morgan, prosecutors said, told witnesses that the deadly shooting of his brother had opened the door for retaliation against “grandmas, mamas, kids and all.”

In the fall of 2015, prosecutors said Corey Morgan, Boone-Doty and other members of their faction of the Black P-Stones street gang were plotting to do just that. In recorded conversations with a jailhouse informant, Boone-Doty allegedly bragged that they had been shadowing Tyshawn’s grandmother, when they saw Tyshawn with his father, Pierre Stokes, an alleged ranking member of the rival Killa Ward subset of the Black Gangster Disciples.

A week after Tracey Morgan was killed, prosecutors say, Boone-Doty opened fire on a Killa Ward member in a parked car, fatally shooting the Killa Ward member’s girlfriend, 19-year-old Brianna Jenkins. In the spring of 2016, on the day Boone-Doty, Morgan and Kevin Edwards were charged with Tyshawn’s murder, Stokes allegedly opened fire on a car holding Corey Morgan’s girlfriend, wounding her and her two passengers. Stokes was arrested days later on attempted murder charges, and is awaiting trial.

Boone-Doty told the jailhouse informant that he had discussed kidnapping and torturing Tyshawn. On the afternoon of Nov. 2, 2015, the alleged killers spotted Tyshawn playing at Dawes Park. Boone-Doty played basketball with Tyshawn, and was seen by witnesses walking off with the boy and his basketball toward an alley off of 83rd Place near South Damen Avenue. Tyshawn, shot in the head at close range, was found in the alley in a pool of blood, his basketball just a few feet away.

Witnesses heard shots and saw a black SUV speed away, with one witness spotting Corey Morgan in the passenger seat. The driver, former co-defendant Edwards, earlier this month entered a guilty plea in exchange for a 25-year prison term.

Boone-Doty and Corey Morgan’s trial is expected to last as long as four weeks in front of a “double jury,” with two sets of jurors to be shuttled in and out of Judge Thaddeus Wilson’s fourth-floor courtroom. Double juries are relatively common in the busy Leighton Criminal Courthouse, allowing two defendants to have separate trials and witnesses to testify only once.

Jury selection began last week, with the panel that will hear evidence against 25-year-old Boone-Doty picked on Friday. Several prospective jurors in the pool to serve on Corey Morgan’s panel let out a groan when Wilson said the trial might last until Oct. 10.