A Chinese man who was arrested in September and admitted to illegally taking photos of a U.S. military installation in Key West, Florida, was sentenced to a year in prison on Tuesday.

Zhao Qianli, 21, pleaded guilty to one count of photographing defense installations. In addition to his prison sentence from a federal judge, Zhao must complete a year of supervised release.

Zhao was arrested on Sept. 26 at the Joint Interagency Task Force South at Naval Air Station Key West. Prosecutors said Zhao was seen taking pictures of sensitive parts of the air station and "associated military hardware" after walking around a fence into a well-marked restricted zone.

Zhao's attorney insisted he was merely a tourist who got lost and wandered onto the base. But investigators say he had only base photos on his cellphone and camera, and no familiar tourist locations in Key West.

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Zhao was in the U.S. to study musicology as part of a summer exchange program from North University of China. The FBI said he was in the country legally, but his visa ran out a week before his arrest.

Fox News' Kathleen Joyce and The Associated Press contributed to this report.