Led by U.S. Representative Duncan Hunter, 21 members of Congress sent a bipartisan letter to Mexico's Attorney General on Thursday calling for the release of jailed U.S. Marine veteran Andrew Tahmooressi.

Tahmooressi, 25, has been held inside La Mesa Prison in Tijuana since April 1, when he was arrested after unintentionally going into Mexico from California's San Ysidro border crossing while carrying three registered firearms. After an escape attempt and having his wounds treated at Tijuana General Hospital following a self-inflicted stabbing, he was placed in the jail infirmary with his arms and legs restrained. He has since been unshackled from the four chains binding him to his cot, and is instead back in the prison with a a chain on one of his legs.

Thursday's congressional letter is a result of mounting pressure, led by the Marine veteran's mother Jill, urging U.S. officials to get involved in Tahmooressi's case. The letter urges Mexico's Attorney General to expedite the young man's proceedings, scheduled on May 28, and dismiss all charges against him. 

"We believe Andrew never attempted to enter into Mexico, and reached a border checkpoint only after missing an exit and mistakenly entering the El Chaparral inspection area," the letter signed by Hunter, Rep. Juan Vargas, Rep. Mario Dias Balart and others. "We fully respect Mexico's right to enforce its laws, but we believe Andrew is not a criminal or a weapons trafficker. He is a Marine Corps veteran who served his country honorably, and simply got lost in an area that he was unfamiliar with."

An active U.S. Marine reservist who served two combat tours in Afghanistan, including a 2010 stint in the violent Marjah district, Tahmooressi was moving to San Diego area with a Marine friend to be close to his treatment center for his post-traumatic stress disorder when he made a wrong turn into Mexico and ended up under arrest.

While on tour in Afghanistan, Tahmooressi suffered a severe concussion when an improvised explosive device (IED) upended his combat vehicle. He now suffers from what his mother, a nurse, calls directional dysfunctionality – frequently getting lost even in areas that he has driven in for years. The Marine reservist was also diagnosed with post-traumatic stress disorder (PTSD) on March 20, with his mother saying he suffered from bouts of depression and hyper-vigilance among other symptoms.

Hunter spoke candidly about the urgency for Mexico to act and drop charges, or the country could expect the same type of treatment to one of its own citizens.

“Perhaps Mexico should be reminded of the hundreds of military and law enforcement incursions at the border, where officials and personnel have entered the U.S. without permission and most always carrying weapons," Hunter said. "These incidents must be stopped altogether, but Mexico’s actions in Andrew’s case, similar to others, underscore the immediate need for a new form of legal treatment by U.S. officials when incursions occur.”

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