A Sydney man, who visited Syria after finishing his studies in a Catholic school, is slated to face eight years in jail for serious terrorism charges if convicted.

John Zakhariev, 21, was arrested in Bulgaria in September 2016, and has been detained in a maximum security prison in Sofia, Bulgaria. Officials believe that he had ties with the jihadist terrorist group.

Zakhariev allegedly tried — and failed — to join the organization four years ago due to his insufficient combat abilities, possessed "jihadist materials," and participated in shooting ranges. His family believes that he is accused of crimes he did not commit.

The son of a Bulgarian-Australian man and a Vietnamese-Australian woman, Zakhariev was raised in Sydney and finished his studies in Waverley College in 2012.

In an interview with Bulgarian media, Zakhariev said that he converted to Islam when he was still a high school student. "When I became a Muslim it was a very emotional time in my life," he shared. "I just broke up with a girlfriend and I had problems with my family ... And it seemed to me at the time that Islam offered something which I really wanted which was companionship and friendship. I have to admit I never really fully believed in Islam."

He returned to being a Catholic in 2016. Hristo Botev, Zakhariev's lawyer, talked about his client's questionable trips and associations to Syria in an interview with Fairfax Media. According to the lawyer, Zakhariev became a member of the Street Dawah when he was 17 years old. The group was led by one Mohammad Ali Baryalei who would go on to become a high-ranking recruiter for the Islamic State.

He travelled to Syria after learning about the situation there to see if he can help. In his eight days in the war-torn country, he stayed in a house under the control of the Jaish al-Mukajireen wal-Ansar, which was not a condemned terrorist organization at the time. Zakhariev left after seeing the violence and brutality of the jihadists.

He went to Europe to take his planned holiday before going back home to continue his studies at the University of Sydney. In 2015, Zakhariev tried to visit Bulgaria, his father's home country, but his passport was confiscated. It was returned after two weeks.

Zakhariev travelled to Bulgaria the following year to help his father return to his home country. Botev admitted that his client went to a legal shooting range, but he refuted that Zakhariev's visit had ill motivations.

Svetlomir, Zakhariev's father and former diplomat at the United Nations, had been supporting the young man through his incarceration until he passed away in late February.

The Australian-Bulgarian student's family expressed their concerns about his situation. "At first, I just thought it was a big misunderstanding, we laughed it off thinking he'd be home in a couple of weeks because he's done nothing wrong," Nevena, Zakhariev's sister, told Fairfax Media. "But as months and months passed, it became more serious. My fear is that the government wants to make an example out of him and he'll go to jail for something he didn't do."

Zakhariev is scheduled to appear at a court hearing on March 17.