A decision is reached in the 2012 shooting of two unarmed individuals in their car after a judge rules on the guilt or innocence of Cleveland police officer Michael Brelo. (McKenna Ewen/The Washington Post)

A Cleveland police officer was acquitted Saturday for his role in the 2012 fatal shooting of two unarmed people in a car after officers mistook the sound of the car backfiring as gunshots.

After a four-week trial, a judge found Michael Brelo, 31, not guilty of two counts of felony voluntary manslaughter in the deaths of Timothy Russell, 43, and Malissa Williams, 30. Russell and Williams were killed Nov. 29, 2012, after they led 62 police vehicles on a chase across Cleveland.

“The state did not prove beyond a reasonable doubt that the defendant Michael Brelo knowingly caused the deaths of Timothy Russell and Malissa Williams, because the essential element of causation was not proved for both counts,” Cuyahoga County Common Pleas Judge John P. O’Donnell said in his ruling.

In downtown Cleveland, protests took place Saturday evening as city leaders called for calm. Police tweeted that they had made “multiple arrests” because of “unlawful behavior by large crowd.” In one incident, police said, a man threw an object through a restaurant window, injuring a woman inside.

The Brelo verdict follows rioting last month in Baltimore over the death of a man who was fatally injured in police custody and comes at a time of growing national scrutiny over the use of force by law enforcement officers, especially against minorities. ­Brelo is white, and the two victims were black.

An animated chronology of events from the end of the police chase to the subsequent shooting. (Ohio Attorney General)

Brelo, a seven-year veteran, is the first of six Cleveland officers to be prosecuted in the fatal shooting. Five police supervisors — none of whom fired shots — each face misdemeanor counts alleging dereliction of duty. No trial date has been set.

When Russell’s Chevrolet Malibu finally came to a stop in East Cleveland, 13 officers opened fire, shooting at least 137 rounds into the vehicle. Brelo, prosecutors said, was the only one who continued to shoot after the threat was over. He climbed onto the hood of the Malibu and shot 15 rounds into the windshield, striking Russell, who was driving, and Williams, who was in the passenger seat.

O’Donnell spent nearly 50 minutes explaining his decision in the bench trial. He walked through the conflicting forensic testimony, using two mannequins in the courtroom to show the trajectory and location of gunshot wounds to the victims. Ultimately, he said, multiple officers fired shots that could have been fatal to the pair.

The officers acted reasonably based upon radio traffic that police were being shot at, he said.

“It is Brelo’s perception of a threat that matters,” O’Donnell said. “Brelo was acting in conditions difficult for even experienced police officers to imagine.”

Brelo, who has been suspended without pay, did not testify.

After the verdict, Brelo cried with his head in his hands. Activists watching from an overflow room chanted, “No justice, no peace.”

Officer Michael Brelo answers questions about the shooting. (Ohio Attorney General)

The judge heard from forensic pathologists, the victims’ siblings, ballistics experts, a mechanic, use-of-force experts and officers.

“We are elated,” said Patrick D’Angelo, one of Brelo’s attorneys. “This has been a blood fight, tooth and nail.”

Stephen Loomis, who heads the Cleveland Police Patrolmen’s Association, said prosecutors had unfairly targeted officers, many of whom did not cooperate with the investigation.

Cuyahoga County Prosecutor Timothy J. McGinty said he was “profoundly disappointed” with the verdict but noted that others face charges in the case.

“The trial forced us to examine how and why so many errors and flawed assumptions could have led to the deaths of two unarmed people,” McGinty said.

The Justice Department began investigating Cleveland police in March 2013 after a string of ­“highly-publicized” use-of-force incidents. The investigation ended in 2014, concluding that the department “engages in a pattern or practice of using excessive force.” Officials with Justice and the city are working to develop reforms overseen by a monitor.

After O’Donnell’s verdict, Justice’s Civil Rights Division, the FBI and the U.S. attorney’s office for the Northern District of Ohio issued a joint statement that they would review evidence from the trial and “collaboratively determine what, if any, additional steps are available and appropriate.” That review is independent of the federal pattern-and-practice investigation, the statement said.

After the ruling, deputies who had been guarding the 18th-floor courtroom rushed to the ground floor, where several dozen protesters were gathered.

Overcome with emotion, Renee Robinson, a cousin of Williams’s, sobbed amid the demonstrators.

“Why? Why? Why?” she said. “My cousin, from my family, she’s never coming back.”

Cleveland Mayor Frank G. Jackson called for calm. Hours later, more than 100 people demonstrated peacefully to mark the six-month anniversary of the fatal shooting of a 12-year-old black child by a white Cleveland police officer.

Tamir Rice was playing with a toy gun in a park when he was shot. County investigators are finalizing their review for prosecutors, who said they will present the evidence to a grand jury.

In recent weeks, other high-profile cases­ involving the deaths of people at the hands of police have emerged. Six Baltimore officers, three white and three black, were charged May 1 in the death of Freddie Gray, a black man who died a week after suffering a ­severe spinal injury in the back of a police van. On April 7, South Carolina authorities charged Michael Slager, a white police officer, with murder in the fatal shooting a black man, Walter Scott, as he ran after a traffic stop.

Prosecutions of officers for the use of deadly force are rare given that there have been thousands of fatal police shootings in the past decade. When criminal charges­ have been pursued, officers have most often been acquitted or cleared, according to a recent analysis by The Washington Post in conjunction with criminologist Philip M. Stinson and researchers at Bowling Green State University.

From 2005 through early April, 54 officers have been charged criminally for shooting and killing someone in the line of duty, the analysis found. Of the 35 cases that had been resolved, 21 officers were acquitted or saw their charges dropped; 11 cases resulted in convictions; and in three cases, the officers entered guilty pleas and were placed on probation. It’s been nearly two years since an officer has been convicted in the fatal shooting of someone in the line of duty.

Brelo is the second officer in Ohio to face charges­ in a decade. The other officer also was acquitted.

The fatal shooting of Russell and Williams in East Cleveland in 2012 was the outcome of a chain of events that began shortly before 10:30 p.m. when an officer in an unmarked car activated his windshield strobe lights and tried to stop the 1979 Chevy Malibu for a turn-signal violation. The blue Malibu stopped but drove off as the officer got out of his car.

About five minutes later, the Malibu backfired as it drove past police headquarters. Officers mistook the sound for gunfire and began to pursue it.

“Old Chevy, on St. Clair just popped a round,” one officer radioed at 10:33 p.m. according to a transcript of radio traffic introduced as evidence at Brelo’s trial. The radio transmission set off what became a 20-mile chase involving more than a third of the 276 Cleveland police officers on duty that night, according to prosecutors.

During the chase, some officers reported that someone was shooting at them from the window of the Malibu. At least one officer reported that was not the case and at 10:47 p.m. radioed: “Passenger just put his hands out asking us to stop. He does not have a gun. He has black gloves on,” the officer said, according to the transcript. “There’s a red pop can in his hand.”

That didn’t stop the pursuit. Seconds later, the Malibu dead-ended into a middle school parking lot and was rammed by an officer’s car. The Malibu spun to a halt as officers began to open fire.

Brelo fired his Glock 17 from his driver’s seat, reloaded and emptied a second 17-round magazine, according to the investigation. He exited his car, according to testimony, to get to a safer position behind another squad car, according to court documents.

A state investigator who interviewed Brelo after the incident testified that Brelo said he drew on his Marine training to “go to an elevated position and push through the target.”

Brelo stepped onto the hood of the Malibu, where he fired 15 shots into the windshield, prosecutors said.

Brelo had told state investigators that he did not recall getting on the hood of the car. At trial, a state forensic scientist testified that he matched photos of footprints on the Malibu to impressions made of Brelo’s boots.

The shooting was over in 17.8 seconds. Russell was shot 23 times; Williams, 24. Prosecutors said evidence showed that Brelo fired 49 times.

Both Williams and Russell were homeless, mentally ill and addicted to drugs, family members and officials said. Police later determined that the pair were under the influence of drugs the night they died.

The pair met in a nursing home where Russell had been undergoing rehabilitation after a car accident in which he “tried to outrun a police car,” his sister Michelle Russell said in court.

Timothy Russell, of Maple Heights, had struggled with drugs and been diagnosed as bipolar, she testified. He was the father of an 18-year-old and was a self-employed bathtub refinisher, a trade he learned after being incarcerated.

Williams, of Garfield Heights, was a sweet girl, said her uncle Walter Jackson Sr. He and his mother helped raise Williams after her mother abandoned her as a child, he said in an interview. As she grew older, she became involved with drugs and was diagnosed with schizophrenia, he said.

Eventually, after repeated bouts with the law, she was imprisoned at a women’s correctional facility in Ohio alongside her mother, he said.

Lowery reported from Cleveland.