WASHINGTON – With a burst of light and dust, an armored vehicle carrying Marines outside a major U.S. air base in Afghanistan erupted into flames, killing three men inside and plunging their unit into chaos.

The April 2019 car bombing about a mile from Bagram Air Base had the hallmark of a coordinated ambush, said two defense officials familiar with the details. A sedan packed with explosives blew up as the Marines' vehicle drew alongside it, mangling the mine-resistant vehicle so badly that U.S. troops had to take the wreckage back to Bagram to extract the remains.

The Taliban released a photo of the explosion afterward, asserting responsibility for it and saying that "multiple invaders" were killed and wounded.

The attack quickly faded from public attention as one of many violent incidents in a war that has killed nearly 2,400 Americans in combat over more than 18 years. But it has been thrust into the spotlight in recent days amid revelations that intelligence analysts believe those who planned it may have been paid a bounty by a Russian military intelligence unit to kill Americans.

President Donald Trump has dismissed the story as a "hoax" amid reports that information about the threat circulated through the American intelligence community and first reached the White House early in 2019, before the attack outside Bagram.

Other Trump administration officials, meanwhile, have cast the information as a concern that merited attention, even if defense officials did not see the intelligence — originally gathered in interviews with Taliban members detained in Afghanistan — as verified.

Caught in the firestorm are the families and friends of the three Marines — Staff Sgt. Christopher Slutman, Staff Sgt. Benjamin Hines and Sgt. Robert Hendriks — who were just a few weeks from returning home to the United States when they were killed.

Kyle Moyer, a Marine veteran who deployed with Hines and Slutman to Iraq in 2008, said that the death of his friends was "heartbreaking" and that the revival of the attack in the news has brought more pain.

"For the immediate family and Marines, it's like ripping a Band-Aid off. They are just getting used to life again. We just had Memorial Day, the one-year anniversary in April, and now this," Moyer said. "They just want the lives to be celebrated, and to remember them, and not have a cloud over it."

Slutman, a 43-year-old married father of three, had served 15 years in the New York City Fire Department. Hines, 31, was engaged to be married when he returned home. The body of Hendriks, 25, was escorted home to the United States by his brother, Joseph, who also is a Marine, his family has said in past interviews.

Several friends, family members and members of their Marine unit either declined interview requests or did not respond to requests. News that Russian officials may have had a role in the attack came as a surprise, the defense officials said, speaking on the condition of anonymity.

Three other service members and an Afghan interpreter were wounded in the explosion.

Hendriks' father, Erik, told the Associated Press that he believes that even rumors of Russian bounties should have been immediately addressed.

"If this was kind of swept under the carpet as to not make it a bigger issue with Russia, and one ounce of blood was spilled when they knew this, I lost all respect for this administration and everything," he said.

The Pentagon has long watched warily as Russia has expanded its involvement in Afghanistan.

Russian officials have accused the United States of supporting ISIS to undermine the Afghan government, a baseless accusation at odds with years of U.S. raids and airstrikes against ISIS and tens of billions of dollars of American aid sent to Afghanistan.

Senior U.S. officials have accused Russia of supplying the Taliban with weapons, including machine guns. Military officials saw the Russian activity at the time as mainly aimed at building relationships with actors who could play a prominent role in Afghanistan's future rather than posing a direct threat to American forces.

Russia has denied the accusation of offering bounties, saying it has supplied weapons only to the Afghan government.

On Tuesday, Defense Secretary Mark Esper said the Defense Department "has no corroborating evidence at this time" to validate the allegations against Russia in Afghanistan, but he said he wanted to assure service members that the department takes seriously "any and all" threats against U.S. troops.

That stood in contrast to the reaction of the president, who dismissed the significance of the reports, citing the lack of Pentagon corroboration.

"Do people still not understand that this is all a made up Fake News Media Hoax started to slander me & the Republican Party?" Trump tweeted on Wednesday. "I was never briefed because any info that they may have had did not rise to that level."

Democratic presidential candidate Joe Biden and other political opponents have said that the situation shows that Trump either read his briefing about the alleged Russian plot and did nothing, or didn't read the intelligence reports.

"Either way, it's an unjustifiable dereliction of duty," Biden tweeted.

Despite the president's dismissal of the allegation, White House national security adviser Robert O'Brien told reporters Wednesday that CIA Director Gina Haspel has distributed "raw intelligence" to coalition forces in Afghanistan "to make sure they have force protection."

The U.S.-led military headquarters in Afghanistan said in a statement Thursday that it doesn't comment on specific intelligence but is "well aware of the potential threats we face from the variety of actors in this complicated region, including the Taliban, ISIS, al-Qaeda and criminal elements looking to disrupt the peace process."

The statement, which did not mention Russia, concluded: "Protecting the force is our top priority, and we regularly review our posture from all standpoints to ensure the protection of our personnel."

On Thursday, Haspel and Director of National Intelligence John Ratcliffe briefed top lawmakers about the intelligence. Congressional leaders shared little about the substance of the briefing, but House Speaker Nancy Pelosi, D-Calif., excoriated the Trump administration as doing too little to ensure the president was aware of the information.

"The White House put on a con that if you don't have 100 percent consensus on intelligence, that … it shouldn't rise to a certain level," she said. "We would practically be investigating nothing if you had to start off at 100 percent. … Just because they didn't have 100 percent consensus, should this be not briefed to the president of the United States?"

Jason Dempsey, an Afghanistan war veteran who studies national security issues for the bipartisan Center for a New American Security, said the stakes in the discussion are "as high as they can be," considering the possible involvement of American deaths.

"The unfortunate thing here is that the grief of these families, which is the most real thing in all of this, will now be used as ammunition in a domestic partisan battle," he said.

Moyer, who lost two friends in the attack, said that no one wants to see the Marines' deaths subsumed by politics.

"They were there serving their country, protecting their beliefs and the country they love, and the freedoms of individuals," he said. "That's how they looked at it, and that's the kind of light they would want put on their deaths, not either party using it to take down a political opponent or justify a political move — anything along those lines."