CLEVELAND, Ohio - Peaceful protests gave way to skirmishes and arrests Saturday, following the acquittal of a Cleveland police officer involved in a deadly 2012 shootout that presented the latest test to a city navigating unprecedented tensions between its citizens and law enforcement.

Mayor Frank Jackson and other city leaders had for weeks prepared for the worst - the possibility of dangerous and damaging riots like those that broke out after other police-community conflicts in Ferguson, Missouri, and, more recently, Baltimore.

For the most part, they got the calm they had urged. Protesters were high on emotion. But in the hours after the verdict, as they moved from the Justice Center and folded into neighborhood demonstrations or resurfaced later in the evening downtown, they remained nonviolent if increasingly disruptive.

Police arrested roughly 40 -- including a Northeast Ohio Media Group editor and two legal observers from the National Lawyers Guild.

Earlier in the day, during the second of two public briefings with Police Chief Calvin Williams Jackson had praised the protesters for being respectful.

"This is a moment that will define us as a city, define us as a people as we move forward and address not only the issues surrounding this verdict, but those things that come in the near future," the mayor said during his first news conference at Public Auditorium.

The city and the U.S. Department of Justice are in the midst of negotiations aimed at reforming police practices. The community also awaits the results of an investigation into last year's officer-involved shooting death of 12-year-old Tamir Rice.

"It is my expectation that we will show the nation that peaceful demonstration and dialogue is the right direction as we move forward as one Cleveland," Jackson said. "We all understand and respect the fact that people have a right to protest and let their voice be heard. However, while we encourage and support peaceful protest, I want to make sure that those who are here that have a different agenda understand that actions that cross the line, whether by police officers or citizens, cannot and will not be tolerated."

The officer, Michael Brelo, stood accused of two charges of voluntary manslaughter in connection with the Nov. 29, 2012 police chase and shooting that killed Timothy Russell and Malissa Williams. After a month-long bench trial and nearly three weeks of deliberations, Cuyahoga Common Pleas Judge John P. O'Donnell found Brelo not guilty on both counts. O'Donnell also determined Brelo was not guilty of the lesser offense of felonious assault, ruling that he was legally justified in his use of deadly force.

Brelo, 31, was among more than 100 officers involved in the 22-minute chase and one of 13 who fired a total of 137 bullets at a 1979 Chevy Malibu. The shooting ended with the deaths of the driver, Russell, and his passenger, Williams. No gun was recovered from the car.

Prosecutors had argued that when other officers stopped firing, Brelo jumped onto the Malibu's hood and shot straight down at Russell, 43, and Williams, 30. Those actions, they argued, were unreasonable and went well past his duties as a police officer.

Race - Brelo is white, Russell and Williams were black - became a flashpoint as Cleveland and other cities across the country face increased scrutiny for the relationship between their police departments and the minority community.

A careful reading and an emotional response

After dark, skirmishes broke out as protesters marched down East 4th Street and engaged with patrons on the city's prime restaurant row. Police led at least three away in handcuffs and other officers in riot gear arrived on the scene.

The disruption resulted in a crackdown by police. From then on, demonstrators squared off with officers in riot gear for several hours in an around downtown's entertainment districts. Police arrested more than a dozen people who they say refused to move or blocked sidewalks and alley ways.

At around 9:45 p.m., several dozen officers pushed through an alley in the Warehouse District between West Sixth and West Ninth streets, chanting, "move back, move back."

After police blocked the alley at both ends, they arrested numerous demonstrators and others in and around the scene, including Northeast Ohio Media Group crime editor Kris Wernowsky, who was recording the demonstration for a live feed on Twitter's Periscope video service.

The arresting officer said that if Wernowsky had a photo identification card to show he is a journalist, he would have been released, as was at least one other journalist with a card. Wernowsky did not have one. The reason for his arrest was not clear. Wernoswky was released around 11:30 p.m.

What's next?

City officials and police will keep tabs on protesters through the holiday weekend. Mayor Jackson will brief the public again at 9 a.m. Sunday, unless significant developments happen before then that would compel him to provide an earlier update.

"So far, the protesters are making their voices heard in a peaceful and respectful way," Jackson said at his final 4 p.m. news conference Saturday.

As for the Tamir Rice investigation, the sheriff has said his department's work is almost done. From there, McGinty will present the case to a grand jury.

And as for Brelo, federal officials said Saturday that they are not done looking at his case.

"We will now review the testimony and evidence presented in the state trial," Vanita Gupta, head of the Justice Department's Civil Rights Division, said in a joint statement with U.S. Attorney Steven Dettelbach and FBI Special Agent in Charge Stephen Anthony. "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."

That review is separate from a Justice Department investigation that found a pattern of excessive force used by Cleveland police. The department is negotiating with the city on a consent decree that would detail how Cleveland will fix such problems.

Northeast Ohio Media Group reporters Brandon Blackwell, Patrick Cooley, Adam Ferrise, Bruce Geiselman, Ida Lieszkovszky, Evan MacDonald, Mark Naymik and Cory Shaffer contributed to this story.

Stay tuned to Cleveland.com for updates as this story develops.