The decision to release him was made by the Korneuburg public prosecutor, spokesman Friedrich Köhl confirmed.
In a statement, the prosecutor said that ballistics and forensic experts had concluded that the shooting could have been an accident, as the accused had claimed, and that there was no conclusive evidence to suggest it was murder.
Köhl said that the investigation into the shooting on September 18th is still ongoing. The case was passed on to the Korneuburg public prosecutor as the accused's ex-wife works for the Vienna public prosecutor and justice officials wanted to avoid any allegations of bias.
On the night of the fatal shooting the 44-year-old banker called the police and said there had been an accident. He told police that his stepbrother had been showing him two guns that he had a weapons permit for, and had accidentally pulled the trigger on one - shooting himself in the head.
Police arrested the banker that evening, saying that he was very drunk. His 42-year-old stepbrother worked for the same bank, and had also been drinking heavily that evening.