Officials are focused on an April 2019 attack on an American convoy. Three U.S. Marines were killed after a car rigged with explosives detonated near their armored vehicles as they returned to Bagram Airfield, the largest U.S. military installation in Afghanistan.
The Defense Department identified them as Marine Staff Sgt. Christopher Slutman, 43, of Newark, Delaware; Sgt. Benjamin Hines, 31, of York, Pennsylvania; and Cpl. Robert Hendriks, 25, of Locust Valley, New York. They were infantrymen assigned to 2nd Battalion, 25th Marines, a reserve infantry unit headquartered out of Garden City, New York.
Slutman was a 15-year veteran of the New York City Fire Department and lived with his family near Wilmington. He was honored in 2014 with the Fire Chief's Association Memorial Medal for rescuing an unconscious woman from a burning high rise.
The 43-year-old also volunteered at the Kentland Fire Department in Prince George's County, Maryland.
"He embodied true character and what it means to serve your fellow man and fellow American," Firefighter Jonathan Clifford of the Kentland Volunteer Fire Department said.
During a previous interview Slutman's dad simply said he hopes the way his son died, does not obscure the way he lived.
"Christopher was a great son. He was a great father. Everything he did, he did well," he said.
Slutman left behind his wife and three daughters.
The White House on Monday said "the veracity" of the bounty reports is still being determined and insisted that President Donald Trump had yet to be briefed on the matter.
"There is no consensus within the intelligence community on these allegations," press secretary Kayleigh McNenay told reporters, "and in effect, there are dissenting opinions from some in the intelligence community with regards to the veracity of what's being reported, and the veracity of the underlying allegations continue to be evaluated."
The New York Times reported Friday that U.S. intelligence officials had determined a Russian military intelligence unit had offered militants tied to the Taliban bounties for killing U.S. and other international troops in Afghanistan.
A military official confirmed to ABC News that U.S. intelligence agencies had determined that to be the case and said Russia had taken the step over the past year, amid peace talks to end the 18-year war in Afghanistan.
President Trump denied that he or vice president had been briefed about the determination, as The New York Times reported Friday.
The Associated Press has reported top officials in the White House were aware in early 2019 of classified intelligence indicating Russia was secretly offering bounties, a full year earlier than has been previously reported, according to U.S. officials with direct knowledge of the intelligence.
The assessment was included in at least one of President Trump's written daily intelligence briefings at the time, according to the officials. Then-national security adviser John Bolton also told colleagues at the time that he briefed Trump on the intelligence assessment in March 2019.
The White House didn't respond to AP's questions about Trump or other officials' awareness of Russia's provocations in 2019.
Bolton declined to comment Monday when asked by the AP if he'd briefed Trump about the matter in 2019.
Hendriks' father told the Associated Press that even a rumor 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," Erik Hendriks said.
Three other service members and an Afghan contractor were wounded in the convoy attack. As of April 2019, the attack was under a separate investigation, unrelated to the Russian bounties.
The officials who spoke to the AP also said they were looking closely at insider attacks from 2019 to determine if they were linked to Russian bounties.
The AP reported the intelligence that surfaced in early 2019 indicated Russian operatives had become more aggressive in their desire to contract with the Taliban and members of the Haqqani Network, a militant group aligned with the Taliban in Afghanistan and designated a foreign terrorist organization in 2012 during the Obama administration.
The National Security Council and the undersecretary of defense for intelligence held meetings regarding the intelligence. The NSC didn't respond to questions about the meetings.
Late Monday, the Pentagon issued a statement saying it was evaluating the intelligence but so far had "no corroborating evidence to validate the recent allegations."
"Regardless, we always take the safety and security of our forces in Afghanistan - and around the world - most seriously and therefore continuously adopt measures to prevent harm from potential threats," said Pentagon spokesman Jonathan Hoffman.
Concerns about Russian bounties flared anew this year after members of the elite Naval Special Warfare Development Group, known to the public as SEAL Team Six, raided a Taliban outpost and recovered roughly $500,000 in U.S. currency. The funds bolstered the suspicions of the American intelligence community that Russians had offered money to Taliban militants and linked associations.
The White House contends the president was unaware of this development, too.
The officials told the AP that career government officials developed potential options for the White House to respond to the Russian aggression in Afghanistan, which was first reported by The New York Times. However, the Trump administration has yet to authorize any action.
The intelligence in 2019 and 2020 surrounding Russian bounties was derived in part from debriefings of captured Taliban militants. Officials with knowledge of the matter told the AP that Taliban operatives from opposite ends of the country and from separate tribes offered similar accounts.
Putin spokesman Dmitry Peskov denied Russian intelligence officers had offered payments to the Taliban in exchange for targeting U.S. and coalition forces.
Secretary of State Mike Pompeo called the Taliban's chief negotiator, a spokesman for the insurgents said Tuesday, but it was unknown whether there was any mention during their conversation of allegations about Russian bounties. Pompeo pressed the insurgents to reduce violence in Afghanistan and discussed ways of advancing a U.S.-Taliban peace deal signed in February, the Taliban spokesman tweeted.
ABC News and The Associated Press contributed to this report.