An act before the person turned 14 may bar execution of the warrant.
Section 74(1)(1) StGB sets the relevant threshold at the fourteenth birthday. Under Section 4(1) JGG, a person who has not yet turned 14 is not criminally responsible for an act punishable by law. If the requested person was under 14 when the particular act occurred, Section 9(1) EU-JZG prohibits execution of the European Arrest Warrant.
Compare the date of birth with the conduct described in the full warrant. Have the documents presented and assessed in the Austrian surrender proceedings.