Original:  By the onset of adolescence, he began exhibiting anti-social behavior . Acquaintances later recalled the young Baumeister playing with dead animals and urinating on a teacher's desk , which are textbook signs of a burgeoning serial killer .
Revised:  By the onset of adolescence, he began exhibiting anti-social behavior by the onset of adolescence, playing with dead animals and urinating on a teacher's desk , which are textbook signs of a burgeoning serial killer .
Edit intent: style