Edgardo Colon and Tyrone Clay are charged with forcible felony and first-degree murder in connection with Dec. 29, 2011 incident.
Two men charged in the shooting death of Chicago police Officer Clifton Lewis were ordered held without bond Saturday.
Tyrone Clay, 29, and Edgardo Colon, 34, are both charged with forcible felony and first-degree murder.
Their arrests came after "basic, tried and true police work" following a recent traffic stop, police Supt. Garry McCarthy said at a Saturday afternoon press conference at the District 15 police station, to which Lewis was assigned.
The case, however, is far from closed, he said.
"We're pleased but we're not even close to being through with this investigation, arrests and prosecution. There is a ton of work to do. This is merely progress in the case. There's a lot more that has to be done," he said.
Officials were careful to not release details that could hamper the department's work, but provided a rundown of what they believe happened the night Lewis was slain.
Lewis was working his part time job at the M&M Quick Foods, at 1201 N. Austin St., Dec. 29 when two masked men walked in with guns drawn to rob the place. One of those men was Clay, said Cook County State's Attorney Anita Alvarez.
Lewis immediately saw the men, drew his weapon and announced that he was a police officer, she said. Clay and the unidentified man opened fire on Lewis, striking him four times; once in the abdomen and three times in the back. Lewis died at the scene, said Alvarez.
After the shooting, Clay took $670 from the cash register while the other gunman took Lewis' weapon. Both then fled the store and got into a waiting getaway car driven by Colon, said Alvarez.
McCarthy said they "can't be clear" as to how many people actually conspired and took part in the crime, but added: "We don't have everybody in custody who we know we want in custody."
Officials said several weapons have been recovered through the course of their investigation. Forensic testing is being done on them to determine if any of them are the murder weapon or if they're linked to other crimes. Lewis' weapon has not been recovered, they said.
McCarthy couldn't confirm if Clay and Colon are gang members, but confirmed the case revolves around a street gang.
"I can assure that group accountability is going to be pursued vigorously, and there will be fallout. We're going to take care of business with that," McCarthy said
Officials said Clay and Colon -- both of whom have prior arrests and convictions -- gave video statements implicating themselves in the crime.
Reached after Saturday's bond hearing, Clay's mother, Lovetta Jones said her son was an innocent man with the mental capacity of someone in their mid-teens and was no where near the store when Lewis was killed.
"He's not a murderer. You know, my heart goes out to that person and may God be with their family and bless their family, but my son is not a murderer," she said.
A woman the Chicago Tribune identified as Clay's girlfriend said outside court that she and Clay were home the night of the robbery and that neither she nor Clay know Colon.
Lewis, a decorated officer who served eight years with the Chicago Police Department, was laid to rest with honors on Thursday.