(CNN) Dr. Lukasz R. Niec was 5 years old when his parents fled Poland with their two children in 1979, his sister says.

Now he's a doctor in Michigan with a family of his own. He was enjoying a day off at his lakeside home near Kalamazoo a week ago when US Immigration and Customs Enforcement agents took him away in handcuffs.

"I'm not sure of anything," Niec told CNN affiliate WWMT from the Calhoun County jail. "I mean, I don't know what's going to happen. It's hard to say, but ... there's a quite a few people in here with different stories. That blew me away. Mine is probably one of the more extreme ones."

Now his family fears he faces deportation to a country he's never known.

"Lukasz doesn't speak Polish. He doesn't have any affiliations to Poland," his sister, Iwona Niec-Villaire, told CNN. "It's not somewhere he feels it's home." Niec received a temporary green card and later became a lawful permanent resident, his sister said.

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