* Gun cleared on one side of border, backfired on the other
* Former Marine still suffers from PTSD from combat in Iraq
* Father flies from Miami to south Texas to pick up son (Adds confirmation of release)
By Tom Brown
MIAMI, Dec 21 (Reuters) - A former U.S. Marine jailed in a notoriously violent part of northern Mexico was released on Friday after being held prisoner four months for possessing a shotgun that was a family heirloom, according to a member of the U.S. Congress.
After speaking with the family of Jon Hammar, U.S. Representative Ileana Ros-Lehtinen of Florida said she was able to confirm the 27-year-old man had been released "and is back safely in the United States."
Olivia Hammar of Miami, the mother of the Iraq War veteran, said Mexican authorities had decided to drop all charges against her troubled son, whose case grabbed the U.S. media spotlight and stirred controversy earlier this month, after determining that he never intended to commit a crime in Mexico.
The decision to release Hammar was announced in a press release on Friday morning from the office of Florida Senator Bill Nelson, who said he got the news from the Mexican Embassy in Washington.
"We're grateful; this is a good Christmas present," Nelson said.
Hammar was heading to Costa Rica to go surfing when he crossed into Matamoros, Mexico, from Brownsville, Texas, in mid-August in a beat-up old Winnebago motor home he and a friend bought especially for the trip.
He had registered the shotgun with U.S. Customs and Border Protection officials on the U.S. side of the border, declaring he planned to take it with him into Mexico.
Despite being told that the shotgun, a Sear & Roebuck model that once belonged to his great-grandfather, posed no problem, Hammar was arrested as soon as he crossed into Mexico. The arrest came when he tried to register the gun with Mexican customs officials, Olivia Hammar said.
The U.S. Embassy in Mexico City said Hammar was charged with possession of a deadly weapon. The family lawyer, Eddie Varon-Levy, had said Hammar faced up to 12 years in prison if he was found guilty.
Making matters worse, Hammar suffers from post-traumatic stress disorder from his combat experience and the death of a fellow Marine who was killed by a sniper's bullet when the two served together in Falluja, Iraq. He had just completed treatment for PTSD at a center for veterans in California last year.
His ordeal in Matamoros, in one of the most violent parts of Mexico, included being shackled to a bed and receiving death threats and extortion demands from drug cartel gangsters who run the prison like their personal fiefdom, Hammar's parents said.
Olivia Hammar said her husband, Jon Hammar Sr., had flown down to south Texas from Miami to pick up his son at or near the prison. (Reporting by Tom Brown and David Adams; Editing by Nick Zieminski and Bill Trott)