Demonstrators were protesting outside the Austin Police Department over the weekend when officers fired a beanbag round, striking a pregnant woman in the crowd.

“My baby!” she cried out in a video that circulated widely online.

The next day, officers again fired a beanbag round — a small projectile that is supposed to be nonlethal but can cause serious injury — as a demonstrator threw rocks and bottles at police. The round struck a 20-year-old black protester standing near the man throwing objects, leaving him in critical condition.

Brian Manley, the city’s police chief, said he was “crushed” by what happened and was praying for the protesters.

“I’ve cried a few times today,” he told reporters.

The incidents in Austin and others like them have echoed in cities across the country since George Floyd’s death last week in Minneapolis triggered a nationwide outcry. Demonstrators opposing police force have been repeatedly met with force, some of it deployed against peaceful protesters, bystanders and journalists — and much of it captured in video footage shared on social media and cable news.

While some incidents have led to discipline for officers involved, the wave of episodes has just as often gone unpunished and prompted still more criticism of law enforcement and questions about why they have reacted by firing gas, rubber bullets and driving into protesters.

Police have said they are under incredible strain, facing violent attacks that include officers being shot, hit by cars or targeted with bricks and fireworks. Police vehicles have also been set on fire and department buildings have been targeted, with protesters in Minneapolis breaching a police precinct last week. In Las Vegas, a police officer responding to demonstrations was shot and seriously injured.

Steve Grammas, head of the Las Vegas Police Protective Association, a police union, said officers were trying to protect the many peaceful protesters, but that sometimes violent elements get involved.

“When I saw pictures of a young girl being tear gassed in the media, it hurt,” he said. “I am a father and it’s gut wrenching. But sometimes — and I hate to say it — there is collateral damage and tear gas meant for the bad ones over spills into the greater crowd.”

While most protests have been peaceful, President Trump and other officials in government and law enforcement have focused on the groups setting fires, looting and causing destruction in footage also relayed across cable news and social media.

Observers say they fear these attacks could escalate the tension on American streets, concerns they say are amplified by Trump’s repeated calls for officials to use much greater force on demonstrators.

“He is supporting violence against the citizens who are protesting,” said Joshua Tepfer, a civil rights attorney in Chicago who has represented clients alleging police misconduct.

In New York and Los Angeles, authorities have pledged investigations after officers were seen driving into demonstrators while also detailing the threats they face. New York Mayor Bill de Blasio (D) was criticized for saying he would not “blame” the officers involved, saying they were dealing “with an absolutely impossible situation.”

Michel Moore, the Los Angeles police chief, said officers were facing difficult decisions in the heat of the unrest. “The people who want us to do something different, what would they have us do?” he said this week. “Have the officers remain there? We’ve seen what’s happened to those vehicles. We’ve seen the smashed windshields.”

On Thursday morning, the Los Angeles police said in a statement they were looking into video footage people had posted online “depicting encounters with the police, that they believe constitutes excessive force or misconduct” amid the demonstrations.

“We will investigate each instance thoroughly, and hold any officer who violates department policy accountable,” the department said.

Officials have also expressed regret for how their departments have responded. Manley, the Austin police chief, said another video from protests there showed a Hispanic teenager struck in the forehead with another less-lethal round — the term for devices like beanbag rounds, which can also cause serious injury.

Manley said that incident, like the others, was being investigated.

“That is not what we set out to do as a department,” he said.

Other incidents around the country have also raised questions about the approach of the police.

In Charleston, S.C., 23-year-old Givionne “Gee” Jordan took a knee during a small daytime protest. Facing nearby police officers with masks down and what appeared to be wooden batons, Jordan spoke passionately and said everyone — police officer or not, black and white — was afraid.

“We are all people,” he said in a video that was posted online. “All of you are my family. All of you are my family. I love each and every one of you. . . . I am not your enemy. You are not my enemy.”

As the video continued, Jordan continued speaking until officers approached him and took him away, while other protesters yelled that they could not arrest him just for speaking.

In an interview Wednesday, Jordan said he had come to the park as part of a group aiming to sweep up the mess left by rioters the night before. He said he wanted other protesters at the park to take a knee to show the police they were peaceful.

Charleston Police Chief Luther Reynolds told the media that the police specifically asked protesters to move many times, warning them they would be arrested if they didn’t leave. In th video, only Jordan was taken away.

Police declined further comment.

“I was just pouring my heart out to them,” Jordan said, adding that police officers treated him well while he was detained. “I wanted to show them a better way. I wanted to be a light in the world.”

Because the video was so widely shared online, “I think I reached some people,” he said.

Activists argue that the more forceful responses nationwide are aimed at silencing protesters.

“The police are attempting to silence Black voices with violence,” Danielle Atkinson, founder and executive director of the group Mothering Justice, said in an email. “We won’t back down because our lives literally are on the line.”

Police are “just reverting to brute force” out of frustration, said Alex Vitale, a sociology professor at Brooklyn College and author of “The End of Policing.”

“On the one hand, they don’t like being vilified,” he said. “They don’t like being resisted [and] there’s a lot of resistance of police happening.”

Top law enforcement officials have pledged that their officers have to respond to what they describe as the dangerous elements seeking to destroy property or steal things.

“Lawlessness has no place in our cities,” David O. Brown, the Chicago police superintendent, told reporters during demonstrations there over the weekend. “And our officers will uphold the law of this country.”

Vitale said the police tactics seen across the country are making the case for protesters out arguing police are out of control.

“Deep down, they [police] understand that there’s a kind of existential crisis at work for them,” Vitale said. “They view the protests as a fundamental indictment of what they do.”

In some cases, police have faced discipline for their actions during the unrest.

Two Atlanta officers were fired after footage spread over the weekend of them pulling two people from a car and using stun guns on them. On Tuesday, prosecutors announced that six officers in total were facing charges over the incident.

An officer in Fort Lauderdale, Fla., was suspended after being filmed shoving a kneeling demonstrator, while a Denver officer was fired after posting a social media photo of himself and other officers in riot gear along with the caption: “Let’s start a riot.”

Other law enforcement officials have faced discipline over deadly uses of force. In Minneapolis, four police officers were fired after the Memorial Day footage emerged of one of them driving his knee into Floyd’s neck while the handcuffed man yelled: “I can’t breathe.” And on Wednesday, authorities revealed that all four now face criminal charges stemming from Floyd’s death.

After law enforcement officials in Louisville shot and killed David McAtee in what authorities described as an exchange of gunfire earlier this week, Louisville Mayor Greg Fischer (D) promptly fired the city’s police chief after learning the officers involved never turned on their body cameras.

Cases where authorities have punished or fired officers are often driven by local political dynamics, said Vitale.

It can be notoriously difficult for departments to punish officers deemed to be engaging in wrongdoing. A Washington Post investigation in 2017 found that over more than a decade, the country’s largest police departments fired at least 1,881 officers for misconduct — and had to reinstate more than 450 of them after appeals.

Janee Harteau, the former Minneapolis police chief ousted in 2017 after a controversial police shooting there, said dismissing troubled officers was a struggle because of the powerful police union.

“I know for me, imposing discipline or terminations were constantly met with grievances,” she said.

The police union president has not responded to multiple attempts to seek comment.

Ronal Serpas, the former police chief in New Orleans and Nashville, said proper internal investigations can be undone through appeals and arbitration. That can tell officers they are unaccountable and make them believe, “You didn’t do anything wrong, we beat them,” he said.

“That’s corrosive among law enforcement,” Serpas said.

Police chiefs leading departments in many big cities — including the District, Boston, Seattle and San Francisco — signed a letter this week saying that not every force can immediately terminate officers.

“Contracts and labor laws hamstring efforts to swiftly rid departments of problematic behavior,” they wrote, calling for a review of both.

The National Fraternal Order of Police responded by saying union contracts are reached between two parties, rather than just imposed by one side, and dismissed the letter as “hand-wringing and deflection.”

“I respectfully suggest that the signatories of the [letter] hold themselves accountable,” Patrick Yoes, president of the group, wrote in his own letter. “Unions do not recruit, hire, train, supervise or discipline our officers.”

Critics said the issue with the police response was broader than a few isolated incidents. Vitale, the sociology professor, said it and Floyd’s death last week were part of a larger issue.

“What happened in Minneapolis with the killing of Floyd was not about a few bad officers,” he said. “And the way that policing of the protests is happening is not about a few bad officers. These are systemic problems.”

Julie Tate contributed to this report.