A San Diego man has been reportedly detained in Iran, and family and friends say they don’t know if he’s even alive. The man, identified as Robin Shahini, is a U.S. citizen and a graduate of San Diego State. “Robin has been known for his advocacy of human rights on social media. This advocacy, unfortunately, has not sat well with the Iranian government,” a friend of his wrote wrote on her Facebook page. He had traveled to the country to visit his mother in Gorgan, about 250 miles northeast of Tehran. Friends said Shahini isn’t an activist, but will occasionally post about human-rights issues over social media. “He just disappeared off the face of the planet. No one knows if he’s alive or dead,” a friend told the Los Angeles Times. “Iran does not recognize Iranian Americans. They believe they’re Iranians and are subject to Iranian law.” Authorities in Iran have already warned Shahini’s mother not to speak to the media, family members said. The U.S. State Department told reporters Thursday it was investigating reports of Shahini’s disappearance but would not comment further on the matter.