The family of a Cuban man arrested on Monday for waving an American flag during the nation’s communist May Day celebration says his whereabouts are unknown. They fear the government has taken him as a prisoner of conscience for his repeated public displays of rejection of dictator Raúl Castro and communism generally.

Daniel Llorente made international headlines on Monday when, moments before the start of Havana’s International Workers’ Day Marxist parade, he ran into an open road, waving an American flag in front of images of mass murderer Ernesto “Che” Guevara. Photos of the man, running before an audience that included Castro and his highest-ranking officials, circulated the globe and inspired anti-communist artwork the very same day.

Government agents attacked Llorente within seconds of his run, beating him and dragging him away.

His whereabouts since he was last seen in public are unknown. Martí Noticias, a U.S.-based Cuban-issues news outlet, contacted members of Llorente’s family, who asked not to be identified for fear of government persecution. “Right now nobody knows anything,” one family member told the outlet on Wednesday. “I hope nothing happens to him and they free him. All I think about is his son, he is in bad shape, his mother died two months ago.”

The U.S. Department of State has urged Cuba to free Llorente. “We know that a protester waving the U.S. flag was detained in the May Day parade in Havana,” spokesman Joseph Crook told reporters. “We call upon the Cuban government to respect the human rights of Cuban citizens, including freedom of expression.”

The May Day protest was the second high-profile act of resistance from Llorente. Last year, the dissident presented himself at Havana’s harbor to greet the Adonia, the first American cruise ship welcomed into Havana by the communist government. Llorente waved an American flag at the ship, shouting, “Yes we can!” as a welcome. His presentation triggered a gathering of communists, who insulted him using racist hand gestures and called him a “clown.”

“I use whatever flag I want because I am free. I am not a hypocrite, not like all the Cubans marching yesterday [the 2016 May Day march] — all those Cubans are hypocrites,” he said, calling the U.S. flag the “pride of the Americans” and stating, “I don’t fear the government.”

Following that incident, Llorente was arrested but released the next day. His prolonged disappearance, and the Cuban government acknowledging his protest Monday, suggest that they view him as a greater threat this year than the year before. The Cuban propaganda outlet Granma published a column on Monday dismissing Llorente as an “annexationist” and criminal, claiming he had served a prison sentence for “armed robbery.”

The relative who spoke to Martí confirmed that Llorente had been in prison for nine years, though the relative said Llorente considered his sentence unfair. “He understood that what they did to him was unforgivable, he got it in his head and that is when he began doing these things, when he got out of prison,” the relative explained. “He said, ‘This government is going to hear me one way or another.”

Llorente is not a member of any Cuban dissident organization and has acted independently to organize his protests.