A man in the front passenger seat of Harris' auto was not injured.
Harris, a 22-year-old from Maryland, was articulated dead at the scene after her sweetheart, who was in the traveler's seat and stayed uninjured, took control of the auto and controlled it to security. The boy was taken to Inova Fairfax Hospital with life-threatening injuries.
Harris was a graduate student studying clinical psychology at Marymount University.
Police say the incident is being investigated as an attempted suicide.
"She was fearless; she was absolutely fearless", he said, according to the Washington Post. She was "caring, compassionate and genuine", Jackson-Cherry said.
Harris' mom told local station WUSA that it was "ironic" the boy who killed her is someone Harris would have helped.
Marymount University officials said support professionals had been made available to students and staff.
Officials said they found nothing mechanically wrong with the vehicle, but were unable to recover information from a water-damaged device on the vehicle that records speed, acceleration and breaking.
However, Harris likely did not have enough time to react, AAA said.
The overpass is set to be replaced when the I-66 express lane project ramps up in the coming months.