CLEVELAND (AP) — A Cleveland patrolman who fired down through the windshield of a suspect's car at the end of a 137-shot barrage that left the two unarmed black occupants dead was acquitted Saturday of criminal charges by a judge who said he could not determine the officer alone fired the fatal shots.

Michael Brelo, 31, put his head in hands as the judge issued a verdict that prompted an angry protest outside the courthouse, including chants of "Hands up! Don't Shoot!"

The acquittal came at a time of nationwide tension among police and black citizens punctuated by protests over deaths of black suspects at the hands of white officers — and following a determination by the U.S. Department of Justice that city police had a history of using excessive force and violating civil rights.

Before issuing his verdict, Cuyahoga County Common Pleas Judge John P. O'Donnell noted the recent unrest in Ferguson, Missouri, and Baltimore over the deaths of black suspects but said he would not "sacrifice" Brelo to an angry public if the evidence did not merit a conviction.

"Guilty or not guilty, the verdict should be no cause for a civilized society to celebrate or riot," he said.

Community and city leaders braced for the possibility of unrest in response to the verdict, which came as investigators work toward making a decision on whether charges will be filed in the death of a black 12-year-old boy carrying a pellet gun who was shot by a white rookie officer late last year.

"We will get justice," said Art McCoy of the Black Man Army, a coalition of black leaders. "We are not happy with this verdict."

One activist, Carol Steiner, said the verdict "wasn't a surprise."

"It's a very bad precedent for Cleveland" with a decision still to come in the death of the 12-year-old, Tamir Rice. "Police murder people of color and not have to serve one day in jail."

The Department of Justice and the FBI said they would review testimony and evidence in the case.

"We will continue our assessment, review all available legal options, and will collaboratively determine what, if any, additional steps are available and appropriate given the requirements and limitations of the applicable laws in the federal judicial system," said the joint statement.

About 30 sheriff's deputies stood in front of the courthouse bearing clear shields as protesters with bullhorns chanted after the verdict. One demonstrator bowed his head with hands folded in front of the phalanx of deputies, praying in silence.

The deputies then moved inside the entrance of the justice center, and the plaza in front of the building was soon cordoned off.

Brelo — who fired a total of 49 shots, including 15 down through the windshield while standing on the hood of the suspects' vehicle — faced as many as 22 years in prison had the judge convicted him on two counts of voluntary manslaughter.

O'Donnell spent nearly an hour summing up his conclusion, an involved explanation that included mannequins marked with the gunshot wounds that the two motorists suffered on Nov. 29, 2012.

O'Donnell said that while Brelo likely fired fatal shots in the final seconds of the encounter in a school parking lot, other officers fired fatal shots as well. Brelo could have been convicted of lesser charges of felonious assault, but O'Donnell determined his actions were justified by the circumstances of the chase, which included reports of shots being fired from the beat-up Chevy Malibu that Timothy Russell was driving.

Brelo's lead attorney, Patrick D'Angelo, told reporters after the verdict his team was "humbled by the verdict but not emboldened by it."

"Officer Brelo risked his life on that night," D'Angelo said, only to be attacked by prosecutors in a case he called a "blood fight."

"I've never in my 37 years witnessed such a vicious and unprofessional prosecution of a police officer," he said.

Cleveland City Council member Jeff Johnson said he totally disagreed with the verdict. "I don't think this community will find this verdict acceptable," he said.

Thirteen officers fired at a car with Russell and Malissa Williams inside after a long, high-speed chase, but only Brelo was charged criminally because prosecutors said he waited until the car had stopped and the pair no longer a threat to fire his final 15 shots.

Russell, 43, and Williams, 30, were each shot more than 20 times. While prosecutors argued they were alive until Brelo's final salvo, medical examiners for both sides testified that they could not determine the order in which the fatal shots were fired.

Brelo has been on unpaid leave since he was indicted May 30, 2014.

The chase and shooting began when Russell's car backfired as he sped past Cleveland police headquarters. Police officers and bystanders thought someone inside had fired a gun. More than 100 Cleveland police officers in 62 marked and unmarked cars got involved in a pursuit that saw speeds reach 100 mph during the 22-mile-long chase.

Authorities never learned why Russell didn't stop. He had a criminal record including convictions for receiving stolen property and robbery and had been involved in a previous police pursuit. Williams had convictions for drug-related charges and attempted abduction. Both were described as mentally ill, homeless and addicted to drugs. A crack pipe was found in the car.

The shooting helped prompt a months-long investigation by the U.S. Department of Justice, which concluded last December that the Cleveland police department had engaged in a pattern and practice of using excessive force and violating people's civil rights. The city and DOJ are currently negotiating a reform-minded consent decree that a federal judge will approve and independent monitors will oversee.

Ohio Attorney General Mike DeWine at the conclusion of a probe by the state Bureau of Criminal Investigation said there had been a systemic failure within the command and control structure of the Cleveland police department during the chase. In addition to Brelo, a grand jury also charged five police supervisors with misdemeanor dereliction of duty for failing to control the chase. All five have pleaded not guilty and no trial date has been set.

Two years after the deaths of Russell and Williams, a white officer fatally shot Rice, the 12-year-old, in a Cleveland park after police received a report of a man with a gun. Surveillance video showed the officer firing on Rice within two seconds of his patrol car skidding to a stop next to him.