LANCASTER>> The Kennett Square man accused of killing his Unionville High School girlfriend in her college dorm room was found guilty Monday of third-degree murder at the end of a nine-day trial.The Lancaster County Common Pleas Court jury deliberated only about one hour before returning with its verdict, which sets up a sentencing hearing later this year for defendant Gregorio Orrosteita in the death of his 18-year-old girlfriend, Karlie Hall, a freshman at Millersville University.