A boom from the Capitol steps sent protesters scurrying back. Stun grenades had begun to rain down on the mob that had laid siege to the U.S. Capitol for nearly three hours.

A man standing on a folding chair on the Capitol lawn raised a middle finger toward the advancing line of police and joined in a chant quickly sweeping the grounds: “Traitors! Traitors! Traitors!”

In a crowd where some carried flags bearing a thin blue line — a pro-police symbol that critics claim also stands for white supremacy and opposition to the Black Lives Matter movement — and shirts adorned with “Blue Lives Matter,” a tide of anger and frustration rose as officers pushed them back. Nearly three hours after the building was breached, police cleared the grounds and used batons and chemical munitions to confront the mob.

“You should be on our side,” a woman in a Trump 2020 sweatshirt called at them. “ ‘We the people’ means police, too!”

“Is this honoring your oath? Pushing patriots around?” another man yelled as an officer shoved him backward with a baton.

Some promised to return with weapons, ready to fight if necessary. A man repeatedly announced he would be back with his rifle for the inauguration of President-elect Joe Biden.

Police experts worry this souring sentiment may lead to more violence in the months ahead. They caution that officers in Washington should prepare to be met with increasing hostility from crowds that previously have clamored for selfies and handshakes from them.

Some Trump allies have speculated that antifa was responsible for inciting violence and storming the U.S. Capitol on Jan. 6. No evidence supports this claim. (The Washington Post)

“In general, the public has this mistaken assumption that the police are there to serve and protect them,” Maria Haberfeld, a professor of police science at John Jay College, said. “The police do what the politicians and other officials tell them to do or not to do.”

Neither D.C. police nor Capitol Police responded to a request for comment.

Conservatives and members of the far-right long have sought to position themselves on the same side of the societal and cultural divide as police. Republicans backed President Trump’s campaign message of “law and order,” and amid rising calls to “defund the police” during racial justice protests last year, the GOP was swift to criticize efforts to shrink police budgets. Police unions and officers vocally supported Trump’s bid for a second term.

But on Wednesday, as the Capitol was being breached and ransacked, people who see themselves as friends of the police were confronted with the reality that law enforcement would not always respond in kind.

“When police have to move against various groups that have supported them, they expect the police to be on their side when they do illegal things, but policing is not really a discretionary behavior,” Haberfeld said. “When people behave the way they behaved at the Capitol, it mandated only one response: Move them out. Arrest them all.”

The law enforcement response, which has been roundly criticized, was tepid compared to police responses to summer protests when demonstrators were arrested en masse. But Trump supporters, who were mostly White, balked at any amount of police resistance Wednesday.

In far-right online forums after the insurrection — during which five people, including a Capitol Police officer, died — Proud Boys, conspiracists, members of armed groups and white nationalists sought to further erode Trump supporters’ veneration of the police by posting videos of officers and rioters exchanging punches and unleashing streams of pepper spray.

“The blue does not back you,” reads a message posted in a pro-Proud Boys group with more than 37,000 followers on social media app Parler. “They back the men who pay them.”

Ashli Babbitt, who was killed during the insurrection, “was shot by cowards protecting traitors,” wrote Jeremy Bertino, a self-described Proud Boy who was one of four people stabbed in D.C. during a chaotic street fight after pro-Trump rallies Dec. 12. “Hang them on the capitol steps.”

Another user commented: “DC blue showed they [chose] a side.”

At a rally the day before the Capitol riot, Cindy Chafian — an organizer with the Eighty Percent Coalition, which sponsored the Tuesday event — told the crowd that it wasn’t police who were keeping them safe, but rather the Proud Boys, anti-government militias and other far-right groups.

“All of those guys keep us safe,” she told a crowd of hundreds.

On Wednesday, three hours after the 6 p.m. curfew by D.C. Mayor Muriel E. Bowser (D) went into effect, a reinforced squad of police officers, Capitol Police officers and National Guard members pushed back a diminishing crowd of Trump’s supporters, who continued to shout abuse at police.

The rhetoric was, at times, similar to far-left protesters who have coined a phrase for police that includes an expletive, while also posting violent anti-police memes in online chats and social media forums.

At racial justice protests over the summer, following a spate of police killings of Black men and women around the country, protesters called police “murderers” and implored officers to join them or take a knee to express solidarity.

But unlike at racial justice demonstrations, where police would fire chemical munitions into areas where protesters were being treated by medics or advance on ailing protesters, several officers at the Capitol on Wednesday seemed sympathetic to the rioters.

Police helped some supporters of the president wash out their eyes after being hit with chemical irritants. At the Capitol gates, some smiled and posed for photos.

Jamie Longazel, who has studied the “Blue Lives Matter” movement since it was formed as backlash to the Black Lives Matter movement, said many of the people who espouse a pro-police ideology are unlikely to change their stripes overnight.

But, he noted, they may make a distinction between the police department of a progressive city like the District — where many officers are Black and Latino — and police of their hometowns.

“I think, for them, seeing the police standing against them probably came as a surprise,” Longazel said. “In their worldview, which is very racialized, they do not see themselves as being part of that savage horde that the police are meant to stand against — no matter what they do.”

Bill Harrison, a 59-year-old supporter of Trump who traveled to D.C. this week from North Dakota, beamed at his wife as the couple walked east from the seat of the U.S. government and darkness fell over the Capitol grounds.

“We just stormed the Capitol,” he said, a tone of awe in his voice.

In truth, he had not stormed the Capitol, only tried.

Along the west security perimeter, Harrison said, he and others had been pepper-sprayed and hit with batons by officers.

“It was wonderful,” he beamed.

Harrison said he has great respect for cops — just not the ones who protect members of Congress.

“These police are protecting the villains inside that building. Somebody back in a small town, that’s my neighbor,” he said. “Here, they’re protecting Schumer. They’re protecting Pelosi.”

Several people in the crowd assailed police officers for protecting the “traitors” inside the Capitol. They beckoned officers to join them, to stand on their “side.”

One woman yelled: “We’re peaceful protesters — do your job and protect us!”

One D.C. police officer in riot gear responded: “Not right now you’re not. Move!”

Nate and Tanya Mitchell, who had traveled to the District from Southern California to show their support for the president, watched from the nearby grass.

They didn’t think the day would have much impact on Trump’s base and its adoration for law enforcement.

The destruction and mob violence at the Capitol a few hours earlier had been the work of a few bad apples, they said. They said they had remonstrated with some of them.

The Mitchells said the police before them in riot gear were just doing their jobs. The couple spoke several hours after the city’s 6 p.m. curfew had gone into effect and were among those defying it — despite a line of police yelling at the stragglers to go home.

“I’m not going home until I feel like going home,” Tanya said.