(CBS News) Jon Hammar, of Palmetto Bay, Fla., survived the wars in Iraq and Afghanistan. Now he's locked up in Mexico, for something his family is calling an honest mistake.
Hammar was arrested this summer after carrying an antique shotgun over the border.
His parents have been desperately trying to free their son ever since.
For the Hammar's parents, the past four months have been a living nightmare.
Jon Hammar, the 27-year-old's father, said, "We just need to get him out before this is too late."
His mother, Olivia Hammar, described the situation as "absolutely paralyzing."
In August, Hammar set out with a friend for a road trip to Costa Rica. It was supposed to be a surfing adventure, a healing getaway for Hammar, who suffers from post-traumatic stress disorder. But he never made it. Crossing from Texas into Mexico, Hammar's parents say U.S. Customs cleared his gun, a family heirloom used for hunting.
Olivia Hammar said, "Customs weighed the gun, measured the gun, I think took pictures of the gun, gave him paperwork to fill out and then he took that paperwork across to the Mexican side, declared the gun, and was immediately arrested."
He was brought to a notoriously dangerous prison near the border. Some say it's run by a drug cartel. There, it's alleged he was chained to a bed.
Olivia Hammar said, "We started receiving calls from members of the cartel that were saying, 'We have your son and we're going to kill him.' And then they'd put him on the phone, so I realized that they really did."
After getting nowhere with Mexico's legal system, the Florida family decided to take their battle public. More than 9,000 supporters have signed an online petition. And now, Capitol Hill has taken up his cause. Sen. Bill Nelson, D-Fla., said from the Senate floor, "Bring this Marine home."
His congresswoman is urging the State Department to step up.
Rep. Ileana Ros-Lehtinen, R-Fla., said, "It's just terrible. This is a Marine hero, a guy that's worn our nation's uniform. He's been deployed many times and this is the way he gets treated?"
She added, "What about our own State Department and Homeland Security -- why aren't they advocating for his immediate release?"
The State Department says officials are in regular contact with Hammar and he's been moved from the general prison population.
In a statement, a spokesman for the Mexican Embassy stressed: "The possession of any weapon restricted for the use of the Army in Mexico is a federal crime ... and must be automatically prosecuted."
Olivia Hammar last spoke with her son on Friday. She recalled, "I said, you know, I really think that something's gonna happen ... and he said 'Mom, you've been telling me that since August.' You know, I don't have a response. Because it's true. I can't make any promises at this point."
Hammar is due in court late next month. If convicted, he faces up to 12 years in prison.
Watch Anna Werner's full report in the video above.