william paul was ` revving his engine ' while sitting alone in the truck sunday when passersby alerted authorities in lexington , kentucky .
paul failed field sobriety tests before being taken to a hospital for facial injuries - authorities say suspects in that situation are not arrested .
paul had two previous alcohol-related run-ins with the law before turning 21 in 2013 .
the 22-year-old is a senior studying communications at the university of kentucky .