"The man has been released because there has not been enough evidence against him to justify keeping him behind bars," his the suspects' lawyer, Philipp Winkler was quoted as saying.
The decision on two other detained suspected is expected to be taken by next week, the police said. The other three suspects including the so called mastermind behind the incident will remain in custody for time being.
The alleged mastermind has sustained a gunshot wound in his head and is reportedly in police custody in an artificially induced coma in a Vienna hospital.
The Vienna police said that the investigator have recovered up to 300 pieces of evidence and that it would at least take a month for the probe to be complete.