Robert Gilman, a U.S. Marine veteran who was imprisoned in Russia for over four years, was nearly on "death's door" before he was this week, according to a hostage crisis expert who advocated for Gilman's release.

The 32-year-old is now in Texas, where he faces a long road to recovery, said Kieran Ramsey, chief investigative officer with Global Reach, an organization that worked to free him.

Gilman, a teacher from Massachusetts, was detained in Russia starting in 2022. Concerns over his health when Global Reach's chief strategy officer, Eric Lebson, said Gilman was being held at a Russian hospital in "dissociative stupor" and being fed through a tube.

"We had to wait 'til almost we were on death's door with him to be able to spur the right kind of action that got his release," Ramsey told CBS News on Thursday. "And we're just thankful he's back on U.S. soil right now."

Gilman is being treated at the Brooke Army Medical Center in San Antonio where he is "getting the world's best medical care," Ramsey said.

Lebson claimed last week that Russian authorities subjected Gilman to mistreatment, including harassment, forced exercise sessions lasting up to 16 hours and the administration of psychotropic drugs. Lebson also alleged Gilman was pressured to fight in Ukraine.

CBS News has not independently verified those claims. Russian officials have not publicly responded.

A State Department spokesperson told CBS News the Trump administration had raised his case with the Russian government repeatedly, and requested he be released on humanitarian grounds, given Gilman's health concerns.

"The situation with Robert is far beyond anything we have seen with any other American detained in Russia," Lebson said.

The Trump administration previously secured the release of several other Americans held in Russia. Multiple others are still being held in the country.

"We have 10 others in Russia," said Ramsey. "We have two designated in Iran. We have one designated in China. Let's hope that he's able to bring all of these folks home as soon as possible."