The teen was arrested and charged after he was identified as one of three people who robbed the officer at a Citgo station.
Devante Graham, 17, was also charged with his cohort's death Thursday based on the theory of accountability after an off-duty Cook County sheriff's sergeant killed a teen when he was robbed by the younger men Monday night at a Citgo gas station in the 700 block of East 103rd Street, authorities said.
The officer was pumping gas when Devante Graham, Deonta Mackey, and a third person approached and surrounded him, Assistant Cook County State's Attorney Claire Savaglio said Thursday.
Armed with a 9 mm semi automatic gun, Mackey, 16, threatened the officer's life, and demanded he turn over his money and everything from his pockets, Savaglio said.
Graham, who had his hands in his pockets, further motioned for the officer to hurry up, Savaglio said.
The officer gave Mackey money and gum while the third offender allegedly went into the officer's car and started rummaging through the glove box.
At that point, Mackey, still pointing his gun at the officer, asked him to give him his wallet and car keys.
That's when the officer reached into his pockets, grabbed his gun and shot Mackey.
Once the shots were fired, Graham and the other person fled, Savaglio said.
The entire incident was captured on nearby video surveillance cameras and the officer identified Graham as one of the men in the trio who robbed him, Savaglio said.
After the shooting, many Chicago Public Schools students told authorities that Graham and his co-offender had posted pictures of themselves with guns on Facebook, Savaglio said.
Upon further investigation, detectives learned that one of the weapons in the pictures was used in the deadly robbery, Savaglio said.
The weapon has been recovered.
Graham, who turned himself into police, is a student at Corliss High School, according to his attorney Donna A. Rotunno.
Outside of court, Rotunno said prosecutors are relying mostly on circumstantial evidence against her client.
"All they have is the video we have all seen," she said.
Graham, of the 10300 block of South Corliss, was found delinquent as a juvenile for aggravated battery in 2010 and for criminal damage to property in 2011.
He was ordered held in lieu of $1 million bond Thursday, the Sun-Times reported.Graham is next scheduled to appear in court March 5.
The 15-year-old is scheduled to appear in bond court Sunday.
The Sun-Times Media Wire contributed to this story.
