Reed was 61 and a resident of Alexandria, Va., said Rachel Reid, a spokeswoman for the Metropolitan Police Department.
Reed's sister found him in his vehicle at the hospital about 8:30 p.m. on May 16. He had been reported missing May 15 when he didn't return from an appointment at the facility, according to The Associated Press.
The veteran was found "slumped over and unconscious," according to a DC police report. A VA medic pronounced the veteran dead before police arrived, according to the report. The VA chief of police and a VA investigator also responded to the scene.
The VA and the House Committee on Veterans' Affairs said they are investigating the circumstances of Reed's death.
A medical examiner is still determining the cause of death. The examiner's office could not be reached by phone Thursday.