Cleveland mayor Frank Jackson answers questions as police chief Calvin Williams watches during a news conference in Cleveland. Jackson was responding to questions about the Cuyahoga County Grand Jury decision not to indict Cleveland police officer Timothy Loehman for the shooting death of 12-year-old Tamir Rice in Nov. 2014.

A grand jury cleared two Cleveland police officers on Monday in the November 2014 fatal shooting of 12-year-old Tamir Rice, who was brandishing a toy gun in a park, and a prosecutor said there were a series of mistakes but no criminal activity.

The decision drew calls on social media for protests around the country and a special prosecutor days after another fatal shooting by Chicago police of two black residents increased pressure on that department and Mayor Rahm Emanuel.

The Ohio grand jury had heard weeks of testimony on the Rice shooting, which occurred within seconds after police reached a park next to a Cleveland recreation center in response to reports of a suspect with a gun. Rice died the next day. The shooting was one of several that have fueled scrutiny of police use of deadly force, particularly against minorities. The officers are white and Rice was black.

Rice was holding a replica handgun when Officer Timothy Loehmann shot him within seconds of reaching the park in a squad car driven by his partner, Frank Garmback.

“Simply put, given this perfect storm of human error, mistakes and miscommunications by all involved that day, the evidence did not indicate criminal conduct by police,” Cuyahoga County Prosecutor Tim McGinty told a news conference. Police radio personnel gave officers a description of the suspect’s clothing but did not convey that a 911 caller had said the suspect was probably a juvenile and the gun may not be real. Those errors “were substantial contributing factors to the tragic outcome,” McGinty said.

On Monday evening, two dozen protesters escorted by police cars walked 3 miles (5 km) in freezing rain from the recreation center to the station where the officers were assigned chanting, “Indict, convict and send the killer cops to jail, the whole damn system is guilty as hell.”

A notice taped to the door said the station was closed. “This is ridiculous,” Terri Tolefree said of the grand jury decision. “This country is so backward.”

Later, a dozen people held hands and prayed in a gazebo at the park where Rice was shot.

Rice’s family has filed a civil lawsuit over his death. It also demanded the officers be charged, a special prosecutor handle the case and the US Justice Department investigate. “Tamir’s family is saddened and disappointed by this outcome — but not surprised,” family attorneys said in a statement. The Justice Department and FBI have been monitoring the investigation and will continue an independent review of Rice’s death, a spokesman said.

McGinty said an enhanced security camera video showed Rice was reaching for the gun, which shoots plastic pellets, when the squad car pulled up next to him.

In a statement to the grand jury, Loehmann said he yelled for Rice to show his hands and saw him pull a gun from his waistband before the officer fired. Loehmann and Garmback also said they were concerned the armed suspect might enter the recreation center.

The officers have been on restricted duty since the shooting and will remain so through an administrative review, police said.

Rice either intended to hand over the gun or show the officers it was not real, McGinty said, “but there was no way for the officers to know that.”

The Airsoft replica of a .45-caliber semiautomatic handgun usually has an orange tip on it, but Rice’s gun did not. Prosecutors showed a standard handgun side-by-side with a replica at the news conference.

McGinty also called on makers of replica guns to do more to make them easier to distinguish from actual firearms.

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