When Russia invaded Ukraine in February 2022, reporters from around the world rushed to the Polish-Ukrainian border to cover an exodus of refugees fleeing Russian bombs.

Among them was Pablo González, a freelance journalist from Spain who had been based in Poland since 2019, working for Spanish news agency EFE, Voice of America and other outlets. Warsaw-based reporters knew him as an outgoing colleague who liked to drink beer and sing karaoke into the wee hours of the morning.

Two and a half years later, he was sent to Moscow as part of a prisoner swap, leaving behind both mysteries about who he really was and concerns about how Poland handled a case in which he was accused of being a Russian agent.

In the first days of the war, González provided stand-up reports to TV viewers in Spain against a backdrop of refugees arriving at the train station in the Polish border town of Przemysl.

But less than week into the war, Polish security agents entered the room he was staying in and arrested him. They accused him of “participating in foreign intelligence activities against Poland” and said he was an agent of the GRU, Russian military intelligence.

Friends were astonished — and, as Poland held González without trial for months that turned into years, some grew sceptical and organised protests in Spain demanding his release. Authorities have never detailed the accusations.

But on Thursday evening, the burly 42-year-old with a shaved head and beard was welcomed home by President Vladimir Putin after being freed in the largest prisoner swap since the Soviet era.

His inclusion in the deal appears to confirm suspicions that González was a Russian operative using his cover as a journalist.

Born Pavel Rubtsov in 1982 in then-Soviet Moscow, González went to Spain with his Spanish mother at age 9, where he became a citizen and received the Spanish name of Pablo González Yagüe. He went into journalism, working for outlets Público, La Sexta and Gara, a Basque nationalist newspaper.

It's not clear what led Poland to arrest him. The investigation remains classified and the spokesman for the secret services told The Associated Press that he could not say anything beyond what was in a brief statement. Poland is on high alert after a string of arrests of espionage suspects and sabotage, part of what the authorities view as hybrid warfare by Russia and Belarus against the West.

Polish security services said Poland included him in the deal due to the close Polish-American alliance and “common security interests”. In their statement, they said that "Pavel Rubtsov, a GRU officer arrested in Poland in 2022, (had been) carrying out intelligence tasks in Europe”.

The head of Britain's MI6 agency, Sir Richard Moore, said at the Aspen Security Forum in 2022 that González was an “illegal” who was arrested in Poland after “masquerading as a Spanish journalist”.

“He was trying to go into Ukraine to be part of their destabilizing efforts there,” Moore said.

Another hint at his activities came from independent Russian outlet Agentstvo, which reported that in 2016 Rubtsov befriended and spied on Zhanna Nemtsova, the daughter of Russian opposition leader Boris Nemtsov, who was murdered in Moscow in 2015.

Poland-based journalists who knew González said he used his base in Poland to travel to former Soviet countries including Ukraine and Georgia. He had a license to operate a drone and used it to film Auschwitz-Birkenau from the air for coverage on the 75th anniversary of the death camp's liberation in 2020.

Voice of America, a US-government funded organisation, confirmed that he worked briefly for them, but they have since removed any of his work from their website.

“Pablo González contributed to a few VOA stories as a freelancer over a relatively short period of time starting in late 2020," spokesperson Emily Webb said in reply to an emailed query. "As a freelancer who provided content to a number of media outlets, his services were arranged through a third-party company used by news organisations around the world."

“At no time did he have any access to any VOA systems or VOA credentials,” Webb said. "As soon as VOA learned of the allegations, we removed his material.”

Because Poland's justice system was politicized under a populist government that ruled in 2015-23, some activists worried about whether his rights were respected. Reporters Without Borders was among the groups that called for him to be put on trial or released.

The group stands by its position that he should not have been held that long without trial. “You are innocent until a trial proves you guilty,” Alfonso Bauluz, the head of the group's office in Spain told AP on Friday. He expressed frustration at the silence around the case, and the fact that there will apparently not be a trial at all, saying Poland has not presented the evidence it has against him.

But the group also says it expects González to provide an explanation now that he is free.

Jaap Arriens, a Dutch video journalist based in Warsaw, hung out with the man he knew as Pablo in Warsaw and Kyiv, as well as in Przemysl shortly before his arrest.

Arriens described him as a friendly, funny man with a macho demeanour and a chest covered in tattoos that he once showed off in a bar.

González mostly fit in, but seemed better-off than the average freelance journalist. He always seemed to have the newest and most expensive phones and computers, working at the Poland-Ukraine border with the latest 14-inch MacBook Pro. He had plenty of money to spend in bars.

He recalled González once saying: “Life is good, life is almost too good.”

"And I thought: Man, freelance life is never too good. What are you talking about?' I don't know any freelancer who talks like this.”

González, whose grandfather emigrated from Spain to the Soviet Union as a child during the Spanish Civil War, was known as a Basque nationalist with ties to the region's independence movement.

Russia is suspected of supporting separatist movements in Spain and elsewhere in an effort to destabilise Europe.

González' wife in Spain had been advocating on his behalf during his detention in Poland, even though they were not living together at the time of his arrest.

Over the past years, the suspect's supporters ran an account on Twitter, now X, to advocate for his release.

When he was sent to Moscow on Thursday, the @FreePabloGonzález account tweeted: “This is our last tweet: Pablo is finally free. Endless thanks to all.”

Those who have followed the case are now awaiting González's next moves.

He has Spanish citizenship — and the right to return to the European Union. His wife was quoted in Spanish media saying she hopes he can return to Spain.