Investigators said Burk had multiple head injuries and believe the cause of death was blunt force trauma. There were no signs that her car was involved in an accident.
Burk left her Los Feliz home around 2 p.m. Friday to drop off paperwork at the Southwestern University School of Law. More than an hour later she called her parents at least two times asking how to get cash using her credit card. Burk was not heard from again.
Investigators believe the teen was killed later that day.
"Lily was looking forward to going to college, to being a writer, to what was ahead," Burk's parents said in a statement. "She had a really bright future, and it was cut short."
Officers said they narrowing in on a suspect and hope to announce an arrest soon.