CHICAGO (CBS) — With the Civilian Office of Police Accountability and Chicago Police Supt. Eddie Johnson unable to agree on whether to fire an officer for fatally shooting two people in 2015, a randomly selected member of the Chicago Police Board will decide the next step.

In December, COPA recommended Officer Robert Rialmo be fired for shooting 19-year-old Quintonio LeGrier and 55-year-old Bettie Jones on the day after Christmas 2015, ruling Rialmo. Investigators said they found no evidence to support Rialmo’s claim the shooting was necessary.

Last month, Johnson rejected COPA’s findings, and in a letter to the agency, stated he had determined “Officer Rialmo’s actions were justified and within Department policy.”

In the two weeks since, Johnson and COPA have been unable to reach an agreement on what disciplinary action Rialmo should face, if any.

The Police Department has acknowledged Jones was an innocent bystander, and was shot by mistake, but has said LeGrier was combative as officers responded to a domestic disturbance call. Rialmo’s attorneys have said LeGrier came at him with a baseball bat, and the officer opened fire in self-defense.

Now the case has been referred to the Chicago Police Board, a civilian body appointed by the mayor to oversee disciplinary action against police officers. The board will randomly choose one member to review COPA’s findings, Johnson’s response, and COPA’s rebuttal. That board member will have 10 days to complete the review.

That board member can either accept the superintendent’s decision that the shooting was justified, ending the case; or side with COPA, and send the matter to the full Police Board to decide whether Rialmo should be fired.

The next Police Board meeting is scheduled for April 19, but the board member reviewing the shooting has until April 25 to review the case. If a decision is reached by the April 19 meeting, the board would discuss it then. Otherwise, the board member’s decision would be announced at the following meeting on May 17.

Rialmo shot LeGrier and Jones at a West Side apartment building in December 2015, just weeks after the release of video of a white police officer fatally shooting 17-year-old Laquan McDonald. The video of Officer Jason Van Dyke shooting McDonald 16 times set off weeks of protests, and prompted Mayor Rahm Emanuel to fire then Police Supt. Garry McCarthy.

On the day after Christmas 2015, Rialmo and his partner were responding to calls about a domestic disturbance at LeGrier’s father’s home. Jones, who lived downstairs, opened the door and directed theh officers to the apartment where LeGrier was staying with his father.

LeGrier, apparently suffering from mental health problems, came running down the stairs with a baseball bat. Rialmo fired eight shots, six of them hitting LeGrier, one of them hitting Jones.

COPA investigators said they found Rialmo’s account of the shooting “inconsistent and ultimately unreliable.” Specifically, the agency said evidence suggested the officer was further away from LeGrier than he claimed when he opened fire.

“We find a reasonable officer in Officer Rialmo’s position would not have believed he was in imminent harm of death or great bodily harm at the time Officer Rialmo began firing his weapon,” the investigators stated.

Legrier was shot dead in the front-entrance vestibule of the apartment building where he was staying with his father. Jones, who was standing behind LeGrier, was killed by a bullet to the chest.

Johnson rejected COPA’s findings in March, calling Rialmo’s decision to shoot consistent with the department’s use of force policies, stating LeGrier attacked Rialmo and his partner “with actions that would likely have caused serious physical injury or death.”

“Further, there is no credible evidence to disprove Officer Rialmo’s perception that Quintonio posed a threat to him as Quintonio advanced toward him. Therefore, it was proper and within Department policy for Officer RIalmo to use his firearm in response to the threat posed by QUintonio, an assailant,” Johnson wrote.

Cook County prosecutors also have reviewed the case, but State’s Attorney Kim Foxx’s office announced in February 2017 that Rialmo would not face criminal charges, citing insufficient evidence to prove Rialmo was not acting in self-defense.