A participant in the San Fermín festival in Pamplona, Spain, who gained viral attention by running the bull run dressed as the Joker, the iconic Batman villain, has been arrested and faces a fine of up to 6,000 euros. Lacey Mrzena, a U.S. citizen from Chicago, was detained by Pamplona municipal police on Saturday after he was caught using a mobile phone to take a selfie in front of the bulls during the run, a serious violation of local safety ordinances.
Video footage released by the municipal police shows Mrzena being intercepted in the sandy arena of the Plaza de Toros by two officers, who then escorted him to the alleyway amid loud jeers from the crowd. The footage clearly captures the American runner at the entrance of the alley with his phone in hand, just a short distance from one of the bulls, at which point he took a selfie. The municipal ordinance governing the bull run classifies the use of recording devices that endanger the safety of runners as a serious infraction, carrying fines ranging from 600 to 6,000 euros.
Mrzena, who has become a phenomenon at the 2026 San Fermín festivities, had been running all the encierros (bull runs) of the year dressed as the Joker. He explained that his choice of costume was motivated by what he called «religious and cultural reasons.» In statements to local media, he said, «It is something cultural. I am very happy. I am not a villain.» He described himself as a lover of Pamplona and the San Fermín festival, as well as an athletic runner.
The arrest highlights the strict safety measures enforced during the world-famous bull run, which attracts thousands of participants and spectators each year. The use of mobile phones or any recording devices during the run is prohibited because it can distract runners and increase the risk of accidents, both for the user and for others. The Pamplona municipal police have been vigilant in enforcing these rules, especially after previous incidents where runners were injured due to distractions.
Mrzena’s case has drawn significant attention on social media, where videos of his Joker-themed runs have gone viral. However, authorities have made it clear that no exceptions will be made for viral fame. The fine, which could reach up to 6,000 euros, will be determined based on the severity of the infraction and any prior record. Mrzena is expected to contest the penalty, but as of now, he remains subject to the legal process in Spain.
The San Fermín festival, held annually from July 6 to 14 in Pamplona, is known for its running of the bulls, a tradition that dates back centuries. Participants run ahead of a group of bulls through the city’s narrow streets, culminating in the bullring. Safety regulations have been tightened in recent years to reduce injuries and fatalities, with police monitoring the event closely. The arrest of Mrzena serves as a reminder that even viral participants must adhere to the rules.
Mrzena’s identity and background have also come under scrutiny. He is a resident of Chicago, Illinois, and has been described as an athletic individual who had completed all the runs of the 2026 festival before his arrest. His motivation for dressing as the Joker remains a topic of curiosity, with his explanation of «religious and cultural reasons» leaving many questions unanswered. Some local commentators have speculated that his costume was a publicity stunt, but no evidence supports this claim.
The incident has sparked debate about the balance between personal expression and public safety during major events. While some festival-goers have expressed sympathy for Mrzena, arguing that his costume added to the festive atmosphere, others have supported the police action, emphasizing that safety must come first. The Pamplona city council has not issued an official statement beyond confirming the arrest and the potential fine.
As the San Fermín festival continues, the case of the Joker runner will likely remain a talking point. For now, Mrzena faces the possibility of a substantial financial penalty, and his future participation in the event is uncertain. The episode underscores the challenges of managing a globally watched event where viral moments can clash with strict safety protocols.