COLUMBUS, Ohio - The Cleveland police union and the local prosecutor remain at odds even after the release of expert reports that found a white officer was justified in fatally shooting a 12-year-old black boy last year.

Cuyahoga County Prosecutor Tim McGinty accuses the Cleveland Police Patrolmen's Association of failing to cooperate with the investigation into the death of Tamir Rice. The union counters that McGinty is just grandstanding.

It is the latest clash between a prosecutor and union who fought over the prosecution of another officer in a racially-charged case in a city under federal scrutiny for how its police force interacts with the public.

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"The union operates by a double standard," McGinty said. "It rightly asks the general public to have the courage to cooperate with police in serious criminal investigations, yet when the conduct of officers is being investigated, refuses to help."

Union President Steve Loomis said McGinty is ignoring the rights that officers have to not give statements during such investigations.

"What he expects us to do, because we're police officers, is just ignore the Constitution," Loomis said Sunday. He added: "We have rights like every other American citizen out there. We have rights just like the bad guys that we're interviewing."

The angry words come despite the release of reports by McGinty that one legal expert said appear to lay the groundwork for a grand jury to not indict any officers in the death of Tamir, who was shot and killed last year outside a recreation center while holding a pellet gun.

"He can come in and hold a press conference, and say, 'I've given the grand jury everything, the grand jury declined to indict, the case is now closed,'" Case Western University law professor Michael Benza said Sunday.

McGinty's office on Saturday released the reports from two outside experts into the Nov. 22 shooting of Tamir by rookie Patrolman Timothy Loehmann.

A lawyer for the family of Tamir Rice lashed out at the release of the reports.

A statement from the family obtained by CBS affiliate WOIO in Cleveland reads: "The family now believes that the prosecutor's office has been on an 11-month quest to avoid providing that accountability. Any presentation to a grand jury--without the prosecutor advocating for Tamir--is a charade. To get so-called experts to assist in the whitewash--when the world has the video of what happened--is all the more alarming."

A retired FBI agent and a Denver prosecutor both found that Loehmann, who shot Tamir moments after the cruiser driven by his partner pulled up beside the boy, exercised a reasonable use of force. They concluded that Loehmann had reason to perceive Tamir - described in a 911 call as man waving and pointing a gun - as a serious threat.

The expert reports came just a few months after another white officer was acquitted in the deaths of two black motorists.

In May, a judge acquitted Michael Brelo on voluntary manslaughter charges in the November 2012 shooting of Timothy Russell and Malissa Williams after Russell's beat-up car backfired outside police headquarters, prompting a high-speed chase with officers who mistook the sound for gunfire. Brelo was accused of firing the final 15 shots of a 137-shot barrage while standing on the hood of Russell's car.

McGinty pushed hard for Brelo's prosecution, though many legal experts thought involuntary manslaughter charges would have been easier to prove.