The next day, the campus police arrested him, while immigration authorities revoked his student visa.

Zhai spent the following four months in jail, which, he said has left him bitter.

"In the first month and a half (in jail), I was refused any contact with the outside world and was given very little food. There was not a single white prisoner there. Bullies robbed my food and beat me when I resisted, leaving my body bruised," Zhai said, pointing to a wound on his right hand.

"Thankfully, an inmate, who was in jail for two weeks for drunk driving, helped me send a message to Wang Meiying, a restaurant owner I once worked for."

Wang hired a lawyer for Zhai and informed his parents, who run a business in Central China's Hunan province.

"In the latter half of my imprisonment, my lawyer Hai Ming and Wang came to visit me regularly. They also deposited some money in my account, which I could use to buy instant noodles in jail," Zhai said.

"My lawyer told me that many Chinese students in the US, who had disputes with their schools, risk having their student visa revoked, being put into immigration prisons or even being deported to China."

After two and a half months in the Hudson County Correctional Center, Zhai was moved to the Elizabeth Detention Center, where suspected illegal immigrants are held.

On July 28, Zhai appeared before the New Jersey Superior Court, where mediation between lawyers and the judge freed Zhai of the charge of making a terrorist threat. But the court slapped him with a charge of disorderly conduct, which Zhai also denied.

A week before Zhai's appearance at the New Jersey court, another charge of aggravated harassment against him was dismissed by the New York County District Attorney's Office.

Zhai left the US on a voluntary departure granted by the federal judge of the immigrant court on July 29.

"I missed my parents a lot in jail," said Zhai, who had not seen his parents for eight years. "I cry every night even after coming back to China. I don't know what's on my mind but I feel angry at the ordeal I endured in the past months.

"But I am ready to go back to the US to prove my innocence if the New Jersey Superior Court opens the case."

Zhai said his idol is Martin Luther King Jr, an iconic figure in the history of American liberalism, best known for his dedication to civil rights.

"I like his 'I Have A Dream' speech. I admire him because he motivated black people in the US to stand up and win political recognition," Zhai said.