Nine days after Russia invaded Ukraine, a prominent banker was thrown from a van in central Kyiv with a gunshot wound to the head.
Denys Kireyev, a Ukrainian, had just returned from Belarus where he had been assisting with peace talks between Russia and Ukraine.
But as he lay dead in the street, rumours quickly spread that Ukrainian intelligence agents had found out he was a spy for Russian President Vladimir Putin.
"During the arrest, the Security Service of Ukraine shot dead Denys Kireyev," Ukrainian MP Oleksiy Honcharenko wrote on his Telegram channel at the time.
"He was suspected of high treason."
His execution appeared to be proof that if Ukraine was going to defeat its aggressive neighbour, it would also have to confront the enemy within.
The Ukrainian state was well aware that Russia had spent years trying to infiltrate its government, intelligence services and military.
Now that Russia had troops on the ground, some Ukrainian officials looked at their colleagues and wondered whose side they were really on.
But nearly a year after Kireyev's slaying, his death is the subject of fierce debate inside Ukraine.
The man killed for being a Kremlin double agent may, in fact, have been a Ukrainian spy all along.
Ukraine's spy chief said Kireyev should be remembered as a hero whose intelligence helped to keep Kyiv from falling into Russian hands.
But who killed Kireyev and why they did it is a mystery yet to be unravelled.
Was it a catastrophic error made in the fog of war? Or did saboteurs within Ukraine's intelligence community want Kireyev dead?
The businessman with a secret
Ukraine has two intelligence agencies that are sometimes locked in direct competition with each other.
The Security Service of Ukraine (SBU) emerged from the ashes of the fearsome Soviet-era KGB when the country became independent in 1991.
But the SBU has sometimes operated under a cloud of suspicion amid concerns that some within its ranks still maintain loyalty to Moscow.
A year after the SBU was formed, the nation's military set up its own spy agency called the Main Directorate of Intelligence of the Ministry of Defence (GUR).
"The GUR enjoys a better reputation than the SBU among foreign partners," US intelligence expert Douglas London wrote in a column for The Hill last year.
"And the GUR has made a more deliberate effort to refashion itself for the times and circumstances."
It is not clear exactly when Denys Kireyev started secretly working for the GUR.
But with his international banking experience, his command of several European languages and his business contacts in Russia, he was an attractive recruit.
The head of the GUR, Major General Kyrylo Budanov, told Radio Svoboda he first met Kireyev in 2009.
"He cooperated with all the former heads of our structure for many years. I met him for the first time when I was still a young officer," he said.
"He passed all the checks here, including the lie detector."
Major General Budanov said that by 2021, as tensions mounted between the nations, Kireyev began monthly trips to Russia under the guise of doing business there.
"He had the necessary circle of acquaintances," Major General Budanov told the Wall Street Journal earlier this month.
"Financial transactions were carried out through him. That's why he had communication with everyone, including very influential people."
According to Major General Budanov, Kireyev's espionage soon paid off.
He was one of Ukraine's first spies to alert the government that Putin's long-threatened invasion could soon come to pass.
In February 2022, Kireyev was meant to join his wife and son on their annual ski trip in the French Alps.
But convinced that an invasion was imminent, Kireyev put his family on a plane and stayed behind.
They would never see him alive again.
How the war blew Kireyev's cover
On February 23, Major General Budanov said he received a tip from Kireyev that would change everything.
Not only did he believe that Putin's invasion of Ukraine was now just hours away, he said Russian troops would use a major airport north of Kyiv to launch their assault on the capital.
Major General Budanov said the intelligence bought the military a few precious hours to scramble their troops to Antonov Airport.
On February 24, as the sun rose over Kyiv, a formation of Russian helicopters advanced on the airfield.
But Ukrainian forces lay in wait.
Using shoulder-fired missiles, they shot down Russian planes and killed hundreds of paratroopers in one of the fiercest battles of the war.
While Russia managed to claim the airport a few days later, the Kremlin's plan for a swift capture of the capital was dead.
The airstrip was trashed and the first chink in Putin's armour was on full display.
"If it were not for Mr Kireyev, most likely Kyiv would have been taken," Major General Budanov told the Wall Street Journal.
Ukrainians realised they were outnumbered and outgunned, but that didn't mean they were doomed to lose.
When Russia and Ukraine agreed to peace talks days after the invasion, neither side expected the negotiations to lead to a ceasefire.
Major General Budanov asked Kireyev to be part of the Ukrainian delegation so they could drag out the process and buy themselves more time to mobilise their defence.
He reluctantly agreed.
When Kireyev walked into the negotiating room in a crisp suit and carrying a leather briefcase, his cover was blown.
Those who believed that he was sympathetic to Russia suddenly realised they were wrong.
"After his appearance there, his connection with the special services became obvious to everyone," Major General Budanov said.
"Unfortunately, the situation then was critical, and we had to take risks."
An execution in the back of a van
Kireyev returned to Kyiv from Belarus on February 29.
Those who saw him in his final days say he was clearly distressed that he'd been exposed as a GUR asset.
A friend said he had started carrying a large hunting rifle around at home because he was worried about who might come to the house to confront him.
Kireyev was meant to return to Belarus for another round of peace talks with Russian delegates on March 3.
But the night before, he was summoned for a meeting with officials from Ukraine's other spy agency, the SBU.
The agency has declined to explain why it wanted to interview him.
When Kireyev and his bodyguards drove to SBU headquarters in central Kyiv, they were suddenly surrounded by a fleet of vans.
"[They] simply broke into the oncoming traffic, operatives ran out shouting, 'It's the SBU,'" Major General Budanov told Radio Svoboda.
Kireyev was arrested just 200 metres from his destination.
"He was transferred to a minibus, which went not to this central SBU building, but several blocks away," Major General Budanov said.
"Then what happened? His body fell out of that van."
The 45-year-old father of a young son was shot dead in the back of a mini-van. His body was dumped in the street.
While local Ukrainian media initially reported the incident as the "elimination" of a Russian agent, Major General Budanov said this was a fake story planted to protect the people who killed Kireyev.
The Ukrainian President's Office has said it believes Kireyev's death was a devastating mistake made in the chaos of war.
It said "poor coordination" between the two intelligence services led the SBU to wrongly conclude Kireyev was a traitor.
But Major General Budanov remains sceptical that it was an accident.
He believes the people who killed Kireyev were trying to disrupt the ceasefire talks in Belarus.
"Whoever did it on purpose wanted to prevent us from interfering in someone else's game," he said last month.
"There was a certain number of people who, let's say, did not really want Ukraine to win. This is my personal opinion."
Four months after Kireyev was killed, Ukrainian President Volodymyr Zelenskyy fired the head of the SBU, claiming Ivan Bakanov had failed to root out Kremlin sympathisers and traitors from the organisation's ranks.
Ukraine has opened 651 collaboration and treason cases against law enforcement officials, including members of the SBU.
"I don't have time to deal with all the traitors but gradually they will all be punished," Zelenskyy said.
The new head of the SBU, Vasyl Malyuk, said the spy agency was undergoing a "systematic cleaning of its ranks".
"I want everyone to realise the SBU is not a place for agents of the Kremlin and people who do not believe in the victory of Ukraine," he said last month.
While Kireyev's death may forever remain shrouded in mystery, he was posthumously awarded a medal for "exceptional duty in defence of state sovereignty and state security".
He was buried with full military honours in a cemetery in Kyiv.
As a spy chief, Major General Budanov is used to keeping secrets. But he said he would continue to speak out in defence of Denys Kireyev.
"I will not allow anyone to spoil the memory of our hero," he said.
