Arturo was married, but having an affair with his secretary, Mónica Gaztambide, and she got pregnant with his son. As one of the hostages, Arturo constantly got himself in trouble due to his attempts to defy the robbers and stage uprisings within the Royal Mint. After the heist, he became something of a celebrity, giving talks about his experience.
When the crew returned to Spain to rob the Bank of Spain, Arturo approached the building and ran inside when the entrance doors were about to close, becoming a hostage again. He tried to manipulate other hostages to go against the robbers, much like in the previous heist. This time, however, the attempts were marred by his predatory behavior towards women; he drugged and raped Amanda, and later tried to do the same to Manila.
Arturo is a coward who tries to escape from severe consequences by letting others do the deeds, putting the other hostages into danger.
He's also a huge attention seeker, as seen in Part 4 where he explicitly states that he wants to be the hero who saves all of them.
He's extremely desperate sexually, making use of women to satisfy his own needs by giving them sleep-inducing anxiety pills.