Following a mass shooting in Philadelphia last week that wounded six police officers and left a neighborhood traumatized, William McSwain, U.S. attorney for the Eastern District of Pennsylvania, broke from tradition. Rather than offering thoughts and prayers for the wounded or promising to keep guns out of the hands of criminals, he railed against a specific actor he holds responsible: Philadelphia’s district attorney, Larry Krasner, widely considered the most progressive prosecutor in the country.

“The crisis was precipitated by a stunning disrespect for law enforcement—a disrespect so flagrant and so reckless that the suspect immediately opened fire on every single officer within shooting distance,” he wrote in a public statement released the day after the shooting. He blamed the attack on “lawlessness” fostered by Krasner and a culture that degrades police officers. Krasner brushed off the diatribe as “a familiar bit of opportunistic politics” from the Trump administration.

The dramatic standoff between a man with an AR-15 and Philadelphia police officers lasted more than seven hours. Police deployed tear gas, and the shooter ultimately surrendered after a series of phone calls with his lawyer, Philadelphia Police Commissioner Richard Ross, and Krasner. No officers were killed, and no bystanders were injured. McSwain was also on the ground.*

The statement was met with surprise; it’s highly unusual for federal prosecutors to openly criticize their local counterparts. But Krasner is no ordinary DA, and McSwain is just one of many “tough on crime” politicians across the country who see him as a threat.

As prosecutors like Krasner gain more traction with voters, they’ve elicited a backlash that now goes all the way up to the nation’s top law enforcement official.

Krasner’s election was the most high-profile success for the progressive prosecutor movement, which seeks to elect district attorneys who recognize the harms of mass incarceration and overprosecution. During his year and a half in office, Krasner, a former civil rights and defense attorney, has used the considerable power of his office to implement policies to reduce rates of incarceration, including amping up the use of diversion programs, scaling back pretrial detainment, and cutting down the length of sentences. He has inspired a growing cohort of prosecutors elected since 2016 on campaigns to reduce rates of incarceration.

This was just the latest chapter in McSwain’s months-long campaign against the Philadelphia DA. He has bad-mouthed Krasner on Fox’s Tucker Carlson Tonight in March and in June, accusing him of causing violent crime to “skyrocket” and tying him to the liberal billionaire George Soros’ “radical agenda.”

In February, McSwain brought federal charges to a gun case after Krasner offered a plea deal he found too lenient. McSwain also claimed in his statement that his office took “70% more violent crime cases this year than we did last year, in response to the District Attorney’s lawlessness.” A spokeswoman for Krasner’s office disputed this, saying she could only find one documented case that could be considered violent where the U.S. attorney filed charges after the DA. McSwain’s office did not immediately reply to a request for data to back up the stat.

“Lawlessness” is a stretch. Overall crime dropped about 5 percent after Krasner’s first year in office, according to NPR. Homicides rose 12 percent, from 315 in 2017 to 353 in 2018, which police officials attribute to the opioid crisis.

As prosecutors like Krasner gain more traction with voters, they’ve elicited a backlash that now goes all the way up to the nation’s top law enforcement official. Last week Attorney General William Barr denounced all reform-minded prosecutors at a national Fraternal Order of Police conference in New Orleans, calling “reformer” DAs “anti–law enforcement DAs.”

Barr, who in 1992 authored “The Case for More Incarceration,” told conference attendees that the rise of “District Attorneys that style themselves as social justice reformers, who spend their time undercutting the police, letting criminals off the hook, and refusing to enforce the law,” is “demoralizing to law enforcement and dangerous to public safety.”

“Once in office, they have been announcing their refusal to enforce broad swathes of the criminal law,” he said. “Most disturbing is that some are refusing to prosecute cases of resisting police. Some are refusing to prosecute various theft cases or drug cases, even where the suspect is involved in distribution. And when they do deign to charge a criminal suspect, they are frequently seeking sentences that are pathetically lenient. So these cities are headed back to the days of revolving door justice. The results will be predictable. More crime; more victims.”

This kind of attack is virtually unprecedented, said David Alan Sklansky, a Stanford Law professor and former federal prosecutor.

Ultimately, McSwain may not be able to do much to stop Krasner from carrying out the promises that won him the election.

“It’s very unusual to see a U.S. attorney take potshots at a district attorney’s approach or a district attorney’s commitment to criminal justice reform. I can’t think of a good analogy or a time I’ve seen something like this,” Sklansky said. “Barr’s comment is pretty unusual as well. Usually prosecutors try to work with each other even when their approaches differ.”

Trump’s Department of Justice has some ability to back up Barr and McSwain’s rhetoric. As McSwain has done, U.S. attorneys can sidestep local prosecutors and bring federal charges in cases that could fall in either jurisdiction. There are overlaps in federal and state laws governing drug and gun charges, for example. So if a local prosecutor’s office decided to stop pursuing certain charges, the U.S. attorney could jump in.

Ultimately, McSwain may not be able to do much to stop Krasner from carrying out the promises that won him the election. The boldest move that McSwain has taken is to file a civil suit against a planned supervised injection site. Krasner and other city leaders support the site, as do district attorneys in other cities across the country including San Francisco, Seattle, and New York City. Trump’s DOJ has made it clear they oppose this type of facility, where people could inject drugs under medical supervision, but McSwain is the first to take the issue to court. The suit is widely considered a test case for jurisdictions also considering a safe injection site.

But reformers say that the most dangerous weapon the feds possess is the bully pulpit. “The attorney general is fanning the flames of fear and returns to the ‘tough on crime’ mentality of the ’80s and ’90s,” said Miriam Aroni Krinsky, the founder and executive director of the group Fair and Just Prosecution. “They can create a narrative like the attorney general has done this week that causes communities to perceive themselves to be unsafe in a way that doesn’t align with what the data tells us, creating fear among residents that causes them to be less likely to embrace smarter and proven approaches.”

Correction, Aug. 21, 2019: This piece originally misstated that William McSwain was not present at the shootout. He was there, his spokeswoman said.