Police have confirmed that the body found was that of Cara. Foul play has been ruled out, which leads me to believe this was either an obvious suicide, or clearly an accident, and that they have evidence to support it. (eg. a note she left. or a witness account of the train conductor seeing her running across the bridge or trying to get off the tracks.)
http://fcpdnews.wordpress.com/2014/09/30/fairfax-city-teen-found-deceased/
Fairfax City Teen Found Deceased
Sully Police District – Fairfax County Police are investigating the circumstances surrounding the death of Cara Lynn Golias,16 of Fairfax City. After an extensive search, Golias was found near the railroad bridge trestle in the 13200 block of Yates Ford Road in the Hemlock Overlook Regional Park at around 1 p.m. on Monday, September 29.
The Office of the Medical Examiner will determine the cause and manner of death, however detectives do not suspect any criminal activity nor public safety threat involved.