Minors under 10-12 cant be persecuted by law depending on eu country.
Every one above can be jailed after juvenile penal law.
In germany this means up to 10 years. Im pretty sure austria has similar juvenile penal laws.
In Austria the limit is 14 years, so if the rapists were under 14 when committed their crime, they can walk away. If they were older, then they going to be prosecuted and will go to a juvenile prison. Of course if they get a liberal judge then they can get off cheaply.
They can walk away without jail time, but not free.
They get sent in reform schools, which are not exactly heavens... It's rather similar to military training! So can't really say he just "walked away freely".
And damn, you not gonna send a 13 years old boy to jail no?