A wrongly deported U.S. citizen who was missing for months in Mexico sued the Department of Homeland Security and the Los Angeles County Sheriff's Department on Wednesday.

Pedro Guzman, 30, who is mentally disabled, was deported last May after he was arrested and jailed on a misdemeanor trespassing charge. For nearly three months, his family searched for him in shelters, jails and morgues in Tijuana, Mexico, and the surrounding area.

During that time, he rummaged for food in garbage cans, washed himself in rivers and walked as far south as Ensenada — more than 60 miles from the U.S.-Mexico border, according to the lawsuit.

Guzman tried to return to the United States several times, but was turned away. He was found near the Calexico border crossing in August and reunited with his family.

"I will never forget what Peter looked like when he finally returned to the U.S. — exhausted and in terrible shape," said Guzman's brother, Michael. "Peter's life is forever changed by what his government did to him."

His lawsuit, which seeks unspecified damages, was filed in federal court in Los Angeles by the American Civil Liberties Union on behalf of Guzman.

"Not only does Peter and his mother want some vindication, they want to make sure immigration officials understand they can't do this," said attorney Jim Brosnahan, who represents Guzman. "They should have apologized and said they would take steps to make sure this doesn't happen again."

A statement released by Immigration and Customs Enforcement, a branch of Homeland Security, called the incident a "one-of-a-kind case" and added more than 1 million illegal immigrants have been deported since the agency's inception.

Sheriff's spokesman Steve Whitmore said he couldn't comment on the specifics of the lawsuit but noted the department followed proper procedures.

"We look forward to telling the whole story," Whitmore said.

The lawsuit claims a sheriff's custodial assistant interviewed Guzman "solely on the basis of his perceived race, ethnicity and national origin." Since 2005, the Sheriff's Department has identified inmates who were eligible for deportation and passed along the information to ICE.

After Guzman was transferred into federal custody, the lawsuit alleges, he was coerced to sign a form written in Spanish that waived his legal rights to a deportation hearing and stated that he was a Mexican citizen.

Guzman "received no assistance from ICE agents — or anyone else — in attempting to read or understand" the form, the lawsuit said.

Guzman's family had filed a previous lawsuit in June when he was missing to force the U.S. government to help find him.

His mother, Maria Carbajal, said her son is improving but hasn't been the same since coming home. She said Guzman wouldn't talk at first and now is afraid of strangers.

"It has affected him emotionally," Carbajal said in Spanish. "Sometimes he disconnects from reality. He was like that before but he's worse now."