Unruly protests against police broke out as officers retreated from their posts in some American cities while others used defense tactics among protesters.

The wide range of responses exacerbated tensions with the protesters in several locations.

The protests came after George Floyd’s death in Minneapolis when a white police officer pressed a knee into the 46-year-old black man’s neck for more than eight minutes on Memorial Day. Floyd was handcuffed as Officer Derek Chauvin pushed his face into the pavement amid his pleas for help.

Tensions rose throughout the week and reached a crescendo Friday night as protests erupted in cities across America. Digitally, viewers saw the extremes in tactics play out all through Thursday and Friday night, even as the majority of cops nationwide tried to keep the peace without retreating or shoving people to the ground.

Minneapolis leaders decided to evacuate a police precinct Thursday and surrender it to protesters who set it on fire. Protesters also broke into the police headquarters Friday in Portland, Oregon, and ignited a fire.

In New York, officers used batons and shoved protesters down as they took people into custody and cleared the streets. One video showed an officer slam a woman to the ground as he walked past her in the street. In Louisville, a police officer fired what appeared to be pepper balls at a news crew, and a clip of the video amassed more than 8 million views on Twitter in less than six hours. Los Angeles police arrested more than 500 protesters on Friday night.

Minneapolis Police and Mayor Jacob Frey have been sharply criticized for the noticeably non-confrontational strategy Thursday in handling the protests after Floyd’s death. Chauvin was arrested Friday and charged with murder.

Some said the act of protesters taking over the evacuated Minneapolis precinct could stoke further flames.

“You’ve got to defend that,” said former Los Angeles Police Deputy Chief Michael Downing. “That’s your command operation. Symbolically, it looks very bad if you have to give that up.”

Downing would know: He witnessed the Los Angeles riots firsthand in 1992 following the acquittal of four officers accused of beating black motorist Rodney King.

The center of the uprising after King’s beating was an intersection, Florence and Normandie avenues, and the violence spiraled into five days of riots and fires. More than 60 people died, including 10 who were fatally shot by law enforcement.

In 1992, then-Lt. Downing would typically oversee that intersection, but he was on vacation studying for a promotional exam. A different lieutenant was in charge instead.

The lieutenant made a decision: He ordered his officers to abandon the intersection. An hour later, a truck driver would be pulled from his vehicle and be brutally beaten by rioters.

“I think that sent a signal to the rest of the city,” said Downing, who immediately rushed to work. “When you have that coupled with political leadership saying, ‘Show your anger. Go to the streets,’ it was kind of like permission to go out and misbehave and be violent.”

Nearly 30 years later, police officers around the country are confronted with an eerily similar dilemma, with cities aflame, violent protests erupting and another challenging night ahead Saturday as National Guard troops start arriving in some cities.

The mere presence of armed National Guard troops on the streets in Minneapolis and elsewhere brings back memories of the civil rights and anti-war protests of the 1960s and ’70s, but the Guard is there only as a support to local law enforcement. The troops do not have the authority to make arrests. They can use their weapons in self-defense but are trained in less lethal crowd control tactics that attempt to de-escalate tensions.

Alex Vitale, a sociology professor at Brooklyn College, said that when deciding how to manage large protests, police and political leaders look for ways to facilitate “legitimate outpourings of anger” while trying to limit the likelihood of injury and property destruction. But he said the difficulty is trying to strike that balance.

“The crisis of police legitimacy has become so great that then to use the police to manage the situation just inflamed the problem,” said Vitale, who has studied the policing of protests for two decades.

In Minneapolis and other cities around the nation where high-profile police killings of black people have prompted protests, the rage felt by protesters is understandable, said Ed Gonzalez, sheriff of Harris County, Texas.

“We see the resulting emotions and anger and calls for change that occur, only for it to happen again.”

Edward Maguire, a criminology and criminal justice professor at Arizona State University who studies policing and violence, said mass arrests are almost always a bad idea during protests. But so is not making arrests in the face of violence and property damage.

He also said police departments should be continuously engaged in building connections with minority communities, faith representatives and social justices leaders so that they have a degree of social capital and open communications when protests break out.

In other recent protests, police found themselves in a similar situation as those on the front lines this week. Police were criticized in Baltimore and Charlottesville, Virginia, for taking too much of a hands-off approach during protests in 2015 and 2017.

In Minneapolis, Frey said he decided to evacuate the precinct that was later torched because of “imminent threats” to both officers and the public.

“Brick and mortar is not as important as life,” Frey said.

Even as law enforcement officials nationwide harshly condemned Chauvin’s actions in unprecedented language earlier in the week, they denounced the violence of the fiery protests and pleaded for calm.

“You can’t allow anarchy just because this horrible injustice has occurred,” said Stephen Downing, Michael Downing’s father and also a retired LAPD deputy chief. “You can’t let your city burn. You just can’t.”

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AP writer Sarah Rankin contributed to this report from Richmond, Virginia.