Notorious Irish criminal John Gilligan has been arrested in Spain after an international drug trafficking investigation.
The crime boss was one of six people arrested during the raid on a residence in Alicante on Friday following an operation by Spanish, Irish and UK authorities.
Police seized four kilograms of cannabis, 15,000 pills, cash, documents and mobile phones, which are all said to be linked to drug trafficking.
A Colt Python revolver was also discovered buried in the garden, and is believed to be the same make and model used to murder journalist Veronica Guerin in 1996.
Spanish police say they are now investigating with Irish counterparts whether this gun is the actual murder weapon.
Footage of Friday's raid was posted to Twitter by police, and shows 68-year-old Gilligan being led away in handcuffs.
It also shows officers unearthing the revolver outside.
In a statement, Policia Nacional said the people arrested were led by a "well-known Irish criminal" and were also part of "a violent group of drug and arms traffickers".
The force added that the group had specialised in "sending illegal merchandise from Spain to the United Kingdom and Ireland through parcels."
According to Spanish authorities, the investigation began last year after the settling of a gang led by "a well-known Irish criminal" in Alicante.
They said on Friday this investigation had resulted in "the total dismantling of the criminal organisation".
Meanwhile, Ms Guerin's brother Jimmy said he was "surprised" over the discovery of the revolver, but was sceptical about the link with his sister's death.
He said: "I think it's speculative but I don't think the Spanish authorities are irresponsible. I'm just sceptical.
"I was informed of the developments before they became public and it has come as a surprise.
"But I'd be sceptical if a gun that was used on the Naas Road turned up in a garden in Spain. Why would you take the risk of bringing it out of the country?"
Gilligan, who was sentenced to 28 years in prison for drug trafficking in 2001, was acquitted of the journalist's murder in the same year after a 43-day trial at the Special Criminal Court.
He was released from prison in 2013.
Judge Diarmuid O'Donovan said at the time of the trial that there were "grave suspicions" about Guerin's involvement in Ms Guerin's death, but said there was not enough evidence produced to bring about a conviction.
