A Pulitzer-Prize winning journalist and filmmaker who outed himself as an illegal alien and went on to become an immigration activist has been released by U.S. Border Patrol agents on Tuesday after they detained him at a Texas airport..

Jose Antonio Vargas, 33, had been in McAllen for several days as part of a vigil to highlight the plight of unaccompanied immigrant children and their families coming into the United States illegally. Given that he released a movie about his life last month and publicized his presence on the border, the self-described "most privileged undocumented immigrant in the country" was likely not surprised at his detention.

“About to go thru security at McAllen Airport,” Vargas tweeted early Tuesday. “I don’t know what’s going to happen.”

Border Patrol spokesman Omar Zamora confirmed that Vargas was in custody, but he had no additional details, The Associated Press reported. However, a spokeswoman for Define American, Vargas' advocacy group, later confirmed his release Tuesday afternoon. Calls seeking comment by FoxNews.com were not immediately returned.

It's common for the Border Patrol to release people on their own recognizances, with notices to appear in court later. With such notices, people can generally travel throughout the U.S. without being detained again. 

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Vargas, who was born in the Philippines, was raised in the United States from age 12. He contributed to The Washington Post’s reporting team that won journalism's top prize for breaking news reporting in 2008 for coverage of the Virginia Tech shooting. More recently, in June, he released “Undocumented,” a film by an “undocumented American” that detailed his experience in the United States.

“An estimated 11 million undocumented immigrants live in the USA,” the film’s poster reads. “One of them made a movie.”

Earlier Tuesday, several immigration groups had demanded Vargas' release.

“We stand in solidarity with Jose Antonio and demand for his immediate release, but we must remember that there are thousands of people along the border that live with this same fear every day,” said Cristina Jimenez, managing director of United We Dream. “Once again, the Border Patrol has proven to be a rogue agency after arresting Jose Antonio, a low-priority case for detention and deportation.”

Luis Maldonado, a McAllen resident whose family is still trapped on the border, also demanded Vargas receive immediate action.

"There are many people in my community, family and close friends of mine that haven't left McAllen in years for fearing detention at one of the numerous checkpoints," Maldonado said in a statement. "I know firsthand the benefits of [Deferred Action for Childhood Arrivals], the simple right to drive to San Antonio without fearing family separation, and I want thousands more in my community to feel the same way."

FoxNews.com's Joshua Rhett Miller and The Associated Press contributed to this report.