TEL AVIV, Israel -- A handful of facts are known about Ben Zygier: He was born Sept. 12, 1976, in Melbourne, Australia, and he died in Israel on Dec. 15, 2010. In between, he was involved in a number of Jewish organizations, immigrated to Israel in his early 20s, married an Israeli woman and fathered two children. He returned to Australia in 2009 to pursue an MBA.

What’s not known is why, in early 2010, Israeli security agents detained him – it’s not clear where – and sent him to solitary confinement in a notorious prison where even his jailers didn’t know who he was or why he was there. Nor is it known how, under 24-hour surveillance in a suicide-proof cell, he managed to hang himself.

Israelis are wondering what Zygier possibly could have done to earn what turned out to be a life sentence in Israel’s Ayalon prison, the country’s highest-security lockup.

His existence became public only upon his death, when an Israeli news website briefly ran an article stating that a prisoner at Ayalon, identified only as Prisoner X, had committed suicide. But that information was quickly put under a censorship order so severe that even mentioning the order itself was forbidden.

The veil finally was lifted Wednesday, when Israeli newspapers were allowed to quote an investigative report by the Australian Broadcasting Corp.

Since then, a few more facts have emerged: Zygier was a member of Israel’s Mossad spy agency. He had multiple identities, including Ben Alon, Ben Allen and Benjamin Burrows.

Friends who remember him in Israel said they called him Benjy, and that he was mostly "a friendly guy, who liked to have a chat."

"He was always keeping up with everything going on around him. He read all the papers and had an opinion about them," said one Israeli who’d served with Zygier in a combat unit. He refused to give McClatchy his name or the year of his service out of fear that he’d be punished for speaking about the sensitive case.

"Everyone is freaked out,” he said. “I mean, I really don’t know anything sensitive or special about him, but the other guys in the unit are all wondering what the hell he could have done. He seemed like a pretty normal guy."

Another friend, who’d attended Zygier’s wedding, told McClatchy there have been "rumors and jokes" that he was a Mossad agent because of his frequent trips abroad and obsession with Middle Eastern politics.

"It was something a few people suspected or whispered about, but it wasn’t really serious. We didn’t think he was some James Bond or anything," he said, also asking to be quoted anonymously.

Israel’s Justice Ministry released a statement Wednesday evening acknowledging the existence of "Prisoner X" for the first time, though it stopped short of naming him. It assured Israelis that whatever Prisoner X had done, due process had been observed at every step: “His family was notified of the arrest immediately. . . . The prisoner was held by proxy of an arrest warrant issued by the court. . . . He was duly represented in all the proceedings against him by attorneys."

The statement concluded: "National security prevents the release of any other details in this case. These aspects of national security have been reviewed by the Central District Court, which decided to impose a comprehensive gag order on the case."