CHICAGO (CBS)Two men were have already been charged with murder in the slaying of a mother in front of her two kids in April, and now, a third man wanted in connection with the murder has been let off the hook.

As CBS 2’s Charlie De Mar reported, the police work in the case of Candice Dickerson, a mother of three. Dickerson was shot and killed as she shopped for a cellphone at the Metro PCS store at 59th Street and Kedzie Avenue on April 26.

The cellphone was going to be a reward for Dickerson’s son for his good grades. The bullet that struck her was fired as part of a gang dispute outside that pierced the store window.

Marco Zabala is accused of supplying the gun in the incident, Bryant Mitchell allegedly pulled the trigger, and an arrest warrant was issued for Carlos Gonzalez’ role.

But on Wednesday, Cook County State’s Attorney Kim Foxx’s chose not to prosecute Gonzalez.

“The public needs to know; the police need to know what happened between the probable cause to arrest and now letting out a guy on a vicious murder involving gang members,” said Martin Preib of the Fraternal Order of Police.

Preib has been critical of Foxx in the past, and questions why Gonzalez was allowed to walk free after an arrest warrant was signed.

“The police did their job on this one. They went out and did their job – -g conducted an investigation, got a warrant signed, and then once again – like the (Jussie) Smollett case and like these exonerations, it gets to Kimberly Foxx’s office and it falls apart,” Preib said.

CBS 2 Legal Analyst Irv Miller said prosecutors likely identified problems before taking this step.

“It sends a message that there was a problem with the case that they probably realized once the arrest warrant was issued,” Miller said. “If you know there’s something wrong, and there’s no longer probable cause, the right thing to do is to go in and get rid of that arrest warrant – and that’s what they did.”

The State’s Attorney’s office providing this explanation: “After a thorough review of the facts and evidence, we declined to pursue charges for Gonzalez.”

Preib fired back: “She needs a better explanation than just having this guy kind of sneak out the back door.”

The other two men are still facing murder charges. But one relative of Dickerson’s told De Mar that she is furious that Gonzalez was let go – saying she feels the justice system failed their family.

Charlie De Mar