Brookman, aged 39, returned voluntarily after surrendering to the Turkish authorities.
The Australian national said he went to the Middle East to render medical assistance to local population.
After being injured in an airstrike, he was taken to a hospital controlled by ISIL Takfiri militants who later forces him to join the terrorist organization, Itar-Tass reported.
However, according to new laws that were recently adopted in Australia, it is a crime to be involved with proscribed militant groups. Being on the territory of Syria or Iraq without the government’s permission is now classified as illegal.
If found guilty, Brookman faces up to 10 years in prison.
According to official statistics, more than 120 Australian nationals have joined extremist groups in Iraq and Syria and 160 more Australians are providing financial and organizational support to terrorists.