Rep. Matt SalmonMatthew (Matt) James SalmonArizona GOP tinkers with election rules with an eye on McCain's seat Quiet jockeying for McCain seat angers Republicans McSally tells GOP colleagues she'll run for Arizona Senate MORE (R-Ariz.) is headed to Mexico to try and negotiate the release of a Marine jailed there for two months on weapons charges.

Sgt. Andrew Tahmooressi was arrested at the beginning of April after he said he took a wrong turn and accidentally drove into Mexico. He was in San Diego to receive treatment for post-traumatic stress disorder after two tours in Afghanistan.

But a wrong turn sent Tahmooressi towards the Mexican border, where border agents arrested him after they discovered several guns in his truck.

Salmon said the arrest was a “terrible mistake,” according to KTAR.

"He crossed over the border not knowing it and was apprehended by Mexican law enforcement officials," he said.

While in Mexico, Salmon will meet with officials from both countries. Several lawmakers, and Secretary of State John Kerry, have mentioned Tahmooressi’s arrest in talks with Mexican officials, and have pushed for his release. Salmon hopes his trip south will be a fruitful addition to that effort.

"He has PTSD, he needs to be treated, he needs to be back with his loved ones and he's not a criminal," said Salmon.

The lawmaker will also be inquiring into the conditions provided to the Marine. Salmon said he had heard reports that Tahmooressi may have been chained to a gurney for weeks, but did not know whether they were accurate.

The Marine’s hearing has been delayed, after he reportedly fired his attorney due to a disagreement about how to handle his case.