The man was struck and killed before 6 a.m. in the southbound lanes of Arlington's Route 110.
The victim in a fatal hit-and-run in Arlington Tuesday morning has been identified as Robert Shepard, 62, of Lawrence, Mass.
Police said he was a veteran with a history of mental illness.
Shepard's girlfriend had reported him missing June 29 in Massachusetts, and authorities there considered him endangered. It's not clear why he was in the D.C. area.
A passing driver called police around 5:35 a.m. Tuesday to report a man lying in a southbound lane of Route 110, in front of a car. The vehicle was gone by the time police arrived, and the victim was pronounced dead at the scene.
Two right southbound lanes on Route 110 were closed to traffic as police searched for personal items, footprints or anything that could explain how the victim came to be in the roadway at the start of rush hour. All lanes have since reopened.
Authorities are trying to determine if Shepard was working with one of two nearby construction crews, or trying to visit Arlington National Cemetery.
What police do know is that the vehicle that struck him was going fast. Shepard was thrown about 60 feet from the point of impact. He was found lying on the sidewalk next to Route 110.
Police say they have some good leads on a suspect, but declined to give details. Anyone with information is asked to call Arlington County Police.
Stay with News4 and NBCWashington.com for more information on this developing story.