Cuyahoga County prosecutor Tim McGinty said during a Monday press conference that he had recommended no indictment to the grand jury. He said Rice's death was the result of a “perfect storm of human error,” not “criminal conduct by the police.”

“We know these charges could not be sustained under the law and our Constitution,” said McGinty. He noted that Rice had been warned earlier in the day that the pellet gun he carried resembled a real gun and said that Rice's “size made him look much older.”

The day before the grand jury released its decision, disillusioned members of Rice's family said they believed it to be unlikely that anyone would be indicted.

Earl Ward, a Rice family lawyer and spokesperson, said Rice's mother was “devastated” by the lack of indictment.

Barricades were set up outside a Cleveland courthouse in case of protests, and a few demonstrators gathered, holding up pictures of Rice and others killed by police around the country.

Unlike criminal trials, in which prosecutors must prove guilt beyond a reasonable doubt for a conviction, the burden of proof for an indictment is much lower. The grand jury had to decide only that a crime might have been committed to indict the officers.

Activists used an obscure state law in June to petition a Cleveland judge to charge the officers. The judge ruled there was probable cause to charge Loehmann with murder and Garmback with reckless homicide based on the video, but he said the decision on criminal charges should be left to prosecutors.

The lead agency investigating the shooting, the Cuyahoga County Sheriff's Office, turned over its findings in June to McGinty.

Investigations and grand jury decisions in other high-profile deaths have come much faster. It took about three months from the time Michael Brown was fatally shot in Ferguson, Missouri, for a grand jury to decide against charges. A grand jury indicted six police officers in Baltimore three weeks after the death of Freddie Gray while in police custody.

The cases come during heightened scrutiny across the United States of police treatment of blacks, after a string of police-inflicted deaths from Ferguson to Chicago sparked protests over the past 16 months. Cleveland police arrested more than 70 people in May during protests after a judge found Patrolman Michael Brelo not guilty of voluntary manslaughter in the November 2012 deaths of two unarmed motorists in a 137-shot barrage of police gunfire after a high-speed chase.

McGinty spokesman Joe Frolik attributed the lengthy investigation in Rice's case to the office being “careful and thorough.”

Grand jury proceedings are supposed to be secret, but McGinty has released expert reports and investigative documents to the media and public while citing his desire for transparency in how the case is being handled.

On the day Rice was shot, a man called 911 to report that a man was waving a gun and pointing it at people. Rice lived across the street from the recreation center and went there to play nearly every day.

The man told the 911 call taker that the holder of the gun was likely a juvenile and that the gun probably wasn't real. The call taker never passed that information to the dispatcher who gave Loehmann and Garmback the high-priority call.

When the cruiser arrived, the vehicle skidded on wet grass and stopped within feet of the boy. Authorities say Loehmann shot Rice less than two seconds after opening the cruiser door.

The officers said they repeatedly yelled at Rice to put his hands up, although investigators found no evidence of that. Garmback said the windows of the cruiser were rolled up.

Experts hired by McGinty concluded the shooting was justified, but separate analyses released by Rice family attorneys concluded otherwise, with one saying the shooting “exhibited a callous disregard for the life of Tamir.”

Experts from both sides testified before the grand jury.

Attorneys representing the Rice family said in a statement Monday that McGinty had spent months “abusing and manipulating the grand jury process to orchestrate a vote against indictment.”

“It is unheard of, and highly improper, for a prosecutor to hire ‘experts’ to try to exonerate the targets of a grand jury investigation,” said the attorneys' statement. “These are the sort of ‘experts’ we would expect the officer's criminal defense attorney to hire — not the prosecutor.”

The boy lay unattended for about four minutes until an FBI agent who is a trained paramedic arrived and began administering first aid.

Despite the lack of an indictment, McGinty said there may still be further legal proceedings revolving around Rice's death.

“The civil justice system may yet provide the Rice family with some of the accountability they deserve,” he said.

Al Jazeera and The Associated Press