The use of tear gas by U.S. authorities on asylum-seekers including small children Sunday builds on a legacy of excessive force at the Southern border, but also represents a reversal of reforms made during former President Barack Obama’s second term toward more humane policies, according to data released by U.S. Customs and Border Protection this week and immigrant rights experts.

Reports of parents and children choking as they ran to escape tear gas at the Mexican border, including a photo of a Honduran mother fleeing the toxic clouds of gas with her twin daughters in each hand, have provoked widespread outrage in recent days.

But the incident has also led to scrutiny of a history of alleged civil rights abuses by Customs and Border Protection, including the use of tear gas for almost a decade.

The Obama administration introduced the use of 2-chlorobenzylidene malononitrile, commonly referred to as tear gas, to the border patrol’s arsenal in 2010.  Exposure to tear gas burns the skin and eyes and makes it difficult to breathe and can leave victims with lasting physical trauma, but law enforcement in the U.S. is permitted to use it for crowd control. 

But immigrant rights experts say the tear gassing of the migrant caravan — comprising men, women and children who have traveled thousands of miles across Central America — represents an immoral and unprecedented ramp up of already brutal treatment of immigrants at the U.S.-Mexico barrier.

“What happened Sunday has never happened before. I was on the border. Trump’s words and actions are pure evil,” said Enrique Morones, who for three decades has worked to protect the health and safety of immigrants with his nonprofit organization Border Angels.

Lawyers who have closely tracked suits alleging the use of excessive force by border patrol say they are unaware of any cases in which children and people seeking safe refuge were the target of tear gas.

Scott Shuchart, who handled allegations of civil rights abuses in immigration enforcement at the Department of Homeland Security for both the Obama and Trump administrations, said such an incident never crossed his desk.

“I am unaware of any other time that tear gas was used on a large crowd known to include small children near the border. If it was, it was not brought to the attention of the DHS Office for Civil Rights and Civil Liberties, to the best of my knowledge,” said Shuchart, who now works as a senior immigration fellow at the Center for American Progress.

Other experts echoed the unprecedented nature of the deployment of tear gas on Sunday.

“I’m not aware of any Obama-era teargassing of asylum seekers,” said Chris Rickerd, policy counsel at the American Civil Liberties Union’s National Political Advocacy Department, who has been critical of violence at border by both administrations.

Customs and Border Protection has alternately defended the use of tear gas as routine and as an action necessary to contain a outsize crisis.

“As CBP has expressed for weeks now, this particular caravan is different from previous caravans — both in the size and the cohesiveness of the group as well as in the aggressiveness of the groups’ conduct in illegally crossing two international borders,” a spokesman said.

Critics, including some government officials, counter that the conflict could have been avoided by properly processing claims for asylum.

“Asking to be considered a refugee & applying for status isn’t a crime,” New York Democratic Rep.-elect Alexandria Ocasio-Cortez tweeted Sunday.

Tear gas use has spiked under Trump to an all-time high of 29 incidents this year, according to data CBP provided, signaling the administration has reversed course on Obama-era reforms.

While border patrol deployed tear gas more than two dozen times during the Obama administration in both 2012 and 2013, the number of incidents nearly halved to 15 in 2014, then declined more to a low of three by 2016.

Rickerd pointed out that the steep drop coincides with several Department of Justice investigations into allegations of excessive violence by law enforcement. Those investigations included a 2014 probe into police departments that deployed tear gas against anti-racism protesters in Ferguson, Missouri.

The same year, Customs and Border Protection revised its use of force manual as part of a “sweeping” set of reforms in order to “fulfill the agency’s commitment to accountability and transparency when officers and agents use force,” according to the agency’s website.

“While far from perfect, these reforms contributed to a reduction in lethal and, at least temporarily, so-called less-lethal uses of force,” Rickerd said.

But the border patrol appears to have abandoned those reforms since Trump assumed office, advocates say.

“President Trump came into office promising that the ‘handcuffs are off’ immigration enforcement agents, and recently incited violence by exhorting military troops at the border to shoot rock-throwers,” Rickerd continued. “Predictably, official violence has ensued and so-called less-lethal uses of force by CBP like tear gas — which is banned on the battlefield yet called ‘very safe’ by Trump — have intensified.”

CBP appeared to share the tear gas data with reporters selectively, releasing it first to conservative media sources more likely to downplay the significance and severity of Sunday’s conflict.

Roll Call inquired about the history of the use of tear gas at 6:30 a.m. Monday. A response came from a CBP spokeswoman at 10 p.m., 10 hours after the right-leaning Washington Examiner published an article citing the same data under a headline sympathetic to the Trump administration, asserting that “Border agents used pepper spray more under Obama than under Trump.” 

Asked about the delay, a spokesman for CBP said agency officials “respond to emails in the order that they are received as quickly as we can.”

DHS and Trump have defended the use of force as a necessary to ward off a foreboding threat. Trump has said that migrants started the fracas on Sunday by throwing chunks of concrete at law enforcement officers. Republicans in Congress have been mum on the incident.

Critics charge the caravan has been unfairly portrayed as violent by White House to reignite immigration as an issue in order to help secure Republican seats during the midterms earlier this month, and help secure more funding for the Department of Homeland Security now.

Trump threatened a government shutdown if Congress does not approve $5 billion in funding for a wall along the Southern border in an interview Wednesday.

“The question should be whether they are responding reasonably to the challenges they are faced with, or if they responding unreasonably. Whether they are solving fake problems or and exacerbating real challenges in order to create a sense of crisis for political reasons and to help in the DHS budget fight on the Hill,” Shuchart said. “It seems very likely that this is what they are doing, and have been doing since before the election.”

Tear gas canisters used in Sunday’s conflict were manufactured by Safariland LLC, according to photos taken at the scene. Public records show the company entered into a contact with Customs and Border Protection in September and will be paid about $500,000 to supply the agency with “non-lethal chemical munitions” through February of next year.

The company did not return a request for comment.