Robert Gilman, a 32-year-old former U.S. Marine who had been jailed in Russia for more than four years, was freed Tuesday after Russian President Vladimir Putin approved a pardon on humanitarian grounds, according to U.S. officials. The release followed weeks of mounting concern from Gilman's family and advocates that he could die in custody. Gilman, from Massachusetts, is a former U.S. Marine who went on to work as an English teacher. The release followed what officials described as intense negotiations over the weekend between U.S. and Russian officials. Kremlin special envoy Kirill Dmitriev also confirmed Tuesday that Gilman had been freed for humanitarian reasons.