MOSCOW — An unidentified assailant detonated an explosive device next to a patrol vehicle in Moscow early Tuesday, killing himself and a police officer, and leaving two other officers injured, officials said.

The attack happened minutes after midnight near the Savyolovsky Train Station in the Russian capital’s downtown, according to Moscow’s branch of the Interior Ministry.

It said the assailant approached a traffic police vehicle and detonated an explosive device, killing an officer on the spot and injuring two others, who were hospitalized.

Russia’s Investigative Committee said it has launched a probe into the attack. It didn’t name the assailant or give any information about his possible motives or any further details.

The attack came on the day marking the fourth anniversary of Russian President Vladimir Putin’s decision to send troops into Ukraine.

Jeanine Pirro’s office has decided to stop pursuing the case against six Democratic lawmakers who urged members of the military and intelligence communities in a social media video not to comply with unlawful orders, three people familiar with the matter told NBC News.

Roughly two weeks ago, as first reported by NBC News, a federal grand jury in Washington, D.C., unanimously rejected an attempt by Pirro, the U.S. Attorney for the District of Columbia, to indict lawmakers over the video, illustrating that grand jurors didn’t think the government had passed even the low legal threshold of probable cause required to bring an indictment.

While a potential case against the six lawmakers is now considered dead in Washington, that decision wouldn’t necessarily bar a federal prosecutor from trying to bring a case in a different federal court district, though there have been no public indications that will happen.

Legal experts and Democrats have criticized the unprecedented attempt to use the immense powers of the Justice Department to punish six members of Congress as a purely political attack on protected free speech and a sign that the guardrails that existed during the first Trump administration have been eroding.

Pirro’s office had tried to charge six Democratic lawmakers, all of whom have military or intelligence backgrounds: Sens. Elissa Slotkin of Michigan and Mark Kelly of Arizona and Reps. Maggie Goodlander of New Hampshire, Jason Crow of Colorado and Chris Deluzio and Chrissy Houlahan of Pennsylvania.

In a series of social media posts, President Donald Trump said the lawmakers were traitors who committed “SEDITION AT THE HIGHEST LEVEL.”

While Trump suggested the lawmakers’ behavior was possibly punishable by death, a grand jury found no evidence of a crime.

Under the Uniform Code of Military Justice, members of the military are obliged to obey only lawful orders and must refuse those that are manifestly illegal.

The lawmakers said after the indictment attempt failed that they wouldn’t be intimidated by efforts to stifle free speech.

“Whether or not Pirro succeeded is not the point,” Slotkin said. “It’s that President Trump continues to weaponize our justice system against his perceived enemies.”

Asked whether Pirro and Trump had spoken about the potential case against the lawmakers, a spokesman for Pirro declined to comment. A White House official said the administration doesn’t comment on potential conversations the president may or may not have had.

Since the Watergate era, administrations of both parties have worked to varying extents to create a firewall between the Justice Department and the White House, allowing the president to broadly set his administration’s policy, but to steer clear of interference in prosecutorial decision-making or even communications that would create an appearance of impropriety.

Former Attorney General Merrick Garland wrote in a 2021 memo that the Justice Department wouldn’t advise the White House on pending or contemplated criminal cases in order to “insulate” leaders from “inappropriate influences,” unless it was “important for the performance of the president’s duties.”

The question of possible political influence on criminal investigations has traditionally been a bipartisan issue. In 2016, when Bill Clinton boarded former Attorney General Loretta Lynch’s plane while the Justice Department was investigating Hillary Clinton’s handling of classified emails, the brief airport tarmac encounter sparked outrage from some Republicans, with Trump himself calling it “so terrible” and “so horrible” and deeming it one of the biggest stories of 2016.

Over the past year, Trump publicly posted a message on social media pressuring Attorney General Pam Bondi to act against a number of his political foes, and he congratulated FBI agents after they raided a Fulton County, Georgia, election center over the 2020 presidential election.

FBI Director Kash Patel put Trump on speakerphone as he cracked open a beverage in the locker room Sunday after the American men’s hockey team won the gold medal at the Milan Cortina Winter Olympics, according to video posted on social media, though the two didn’t discuss any investigations while Trump was on speakerphone with the hockey players.

Pirro, a former Fox News host, has a decadeslong relationship with Trump, who named her the top federal prosecutor in Washington after Senate Republicans bristled at the nomination of Ed Martin, a longtime conservative activist and advocate for Jan. 6 rioters who led the “Weaponization Working Group” and continues to hold the position of Justice Department pardon attorney.

“She is in a class by herself,” Trump wrote when he nominated Pirro. “Congratulations Jeanine!”

In the days before attorneys working for Pirro presented the case to a federal grand jury, Pirro made more than a dozen posts praising Trump, though she never publicly spoke about the case against the lawmakers or tied it to Trump. One post read that criminal cases were being brought “Under the directive of @POTUS.” On Monday, she posted a video recorded “right outside the White House” in which she praised Trump.

And last week, massive banners featuring Trump’s likeness were hung up on the outside of Justice Department headquarters.

The New York Times reported last week that Pirro “abruptly” told her team to seek the indictment.

In a Feb. 5 letter to Pirro that copied two attorneys who tried to bring the case, Carlton Davis and Steven Vandervelden, former U.S. Attorney Preet Bharara — representing Slotkin — wrote that it was “perplexing” that the Justice Department had brought an inquiry into the matter. The letter mentioned that he had spoken to Pirro’s “special counsels” on Jan. 14 and one on Jan. 27.

“The prosecutors we spoke to in your office, though courteous, could not articulate any theory of possible criminal liability or identify any statute they were relying on that could have been violated,” he wrote, as first reported by The New Republic.

Pirro’s office cannot comment on grand jury matters.

Bharara later wrote in a letter to Pirro that the grand jury had spoken “loudly, clearly, and unanimously” and said continuing to pursue the matter would be a violation of Justice Department policy.

Paul Fishman, a former U.S. attorney who is representing Kelly, wrote in a letter to Pirro’s office that trying to seek an indictment again “would be a remarkable abuse of the Department’s power.”

“This guy thought I would be in in jail,” Kelly told reporters Monday. “Wants to send me to prison.

Still, he said he would attend Trump’s State of the Union speech Tuesday. “I’m gonna continue to do my job, and I’m going to be sitting there right in front of him, he said. “You know, maybe he’ll notice, maybe not, but I feel it’s my obligation, you know, to be there.”