More than three-dozen of Hammar’s friends gathered at Ros-Lehtinen’s office Thursday, wearing yellow ribbons to support military families. Classmates of Hammar’s sister, who has not been able to come home yet because she’s taking college exams in North Carolina, said they have decorated trees at Westminster with messages for Hammar.

“Everybody loves him,” 22-year-old Brittany Hays said of Hammar, whom she has known for more than a decade.

Several friends called Hammar kind-hearted and easygoing, with a surfer’s long locks and laidback demeanor. As a kid, Hispanic friends nicknamed him Juan Martillo — a play on the phonetic sound of his name, “John Hammer.” In high school, a string of girls had crushes on him. He loved the water and volunteered teaching disabled children how to sail, a high school classmate and neighbor said.

After the 9/11 terrorist attacks, Hammar and a group of friends enlisted in the Marine Corps. He was deployed to Afghanistan and Iraq, where his battalion lost more than a dozen troops, before receiving an honorable discharge in 2007. He later served four more years in inactive reserve.

Last year, Hammar voluntarily checked into a residential treatment center for veterans in California, where he was treated for nine months for PTSD. (His mother said he complained that the California surf was too cold. “I’ve got to move back to Miami,” he told her.)

In prison, Hammar has reverted to “combat mode,” said his mother, who calls her son Jonny.

“In addition to being somewhat hopeless, he is enraged,” she said. “He’s read the entire Bible, because that’s all he has.”

Olivia Hammar, a magazine publisher, said she Googles news about Mexico every morning to find out of anything violent has happened at or around the Matamoros prison. She expected Hammar to return from Mexico in September, when her husband, a software engineer also named Jon, traveled to Matamoros to fight for his son’s release.

“It’s a precarious situation now that we’ve gone public,” Jon Hammar said, calling for an end “to this silly, unfortunate thing that is happening.”

Hammar’s friends, hoping for his return by Christmas, are planning a celebration on Dec. 26. Also in the works: a plan to raise money to send Hammar to Costa Rica — on a plane.

“We’re just so proud of everything that he’s done,” friend Jessica Fernandez said. “We’re not going to rest until he comes home.”