33-year-old Deni Vasilyev had lived in Austria for almost ten years, after fleeing Belarus and claiming asylum here.
He is believed to have travelled across Germany to Turkey and from there into Syria to join fighters with the so-called Islamic State group - but it is not clear when he arrived in Syria.
A report on the Kurdish news website ANF-News said that Vasilyev's body was found with his Austrian residence permit, his health insurance e-card and the business card of a dentist in Bregenz.
Vasilyev had taken a course to become a crane and forklift operator in Austria in 2010. The course fees had been paid by the Catholic organization Caritas, as he was unemployed at the time.
In 2010 he took part in a refugee day in Bregenz, and acted out the part of a border guard in a drama designed to show people what life as a refugee is like.
It is not clear when he became radicalized, and state security head Erich Schwärzler told the Vorarlberger Nachrichten that he would discuss the issue with the police intelligence agency on Wednesday.