Australian-born Israeli Mossad operative Ben Zygier, who killed himself in an Israeli prison cell in December 2010, had inadvertently leaked sensitive information that led to the arrest of informants spying on Hezbollah in Lebanon, the German paper Der Spiegel reported on Sunday.

According to the report, Ben Zygier was arrested in Israel because he was suspected of unwittingly passing on information to a Hezbollah operative that led to the arrests in Lebanon of Siad al-Homsi and Mustafa Ali Awadeh in 2009. Both men were later sentenced to 15 years in prison for spying for Israel.

Zygier, a Jewish man from Melbourne, was trying to prove his mettle to the Israeli spy agency in an effort to regain face after failing to fulfill expectations during an operation in Europe, the German report said.

Zygier made international headlines in February 2013, when details of his clandestine incarceration and later suicide finally emerged, over two years after he took his own life in an isolated cell in Israel. Before that, there were rumors in the Israel media regarding a mysterious “Prisoner X,” who was being held under absolute secrecy in the Ayalon prison.

According to the report, Zygier, who was apparently recruited by the Mossad spy agency in 2003, was sent to Europe in 2005 to infiltrate companies that were dealing directly with Iran. Zygier’s mission was to try to gain access to potential informants in Iran and Syria. However, after two years, during which he was employed in the accounting division of a company, Zygier was recalled to Israel without having achieved substantial results.

Zygier, disappointed, was assigned a desk job but still hoped to find his way back into the field, Der Spiegel reported. Apparently acting on his own initiative, he began trying to recruit informants in Lebanon to spy on the Hezbollah terror organization. He contacted an affiliate of the group in a Balkan state and tried to recruit him. However, the Hezbollah activist succeeding in turning the tables and duped Zygier into providing information that eventually led to the arrests of al-Homsi, Awadeh, and a string of other informants in Lebanon.

Meanwhile, after spending a year behind a desk, Zygier asked for permission to continue his academic studies in Melbourne, and in 2008 he began a graduate degree in Monash University. During the period of his studies, Zygier was apparently indiscreet about his activities with the Mossad, which eventually learned he was leaking details of his service, some of them inaccurate. Zygier was called back to Israel to face an investigation during which details of his unauthorized solo Hezbollah operation came to light. He was subsequently arrested, incarcerated under strict secrecy, and charged with what one of his lawyers said last month with “serious” crimes.

Israeli authorities reportedly sought a prison sentence of up to 10 years for the offenses. A plea bargain was under discussion when Zygier, who was 34 and married with two children, took his own life by hanging himself with a bed sheet in the shower on December 15, 2010.

Amid myriad speculations and theories regarding the Zygier case and his alleged crimes, none of which suggested deliberate treason, Israeli authorities have remained tight-lipped over the precise details of the story.