The drum was either knocked over or dislodged from a piece of heavy equipment, police said. It then rolled several hundred feet as it went down a hill, through a fence and onto the sidewalk where the woman was walking with co-workers from the University of Pittsburgh Medical Center's Western Psychiatric Hospital.
Police say an 18-year-old man was killed, and a 23-year-old and two 17-year-olds were wounded in what they believe was a drive-by shooting. One of the 17-year-olds is in critical condition.
The Office of Army Cemeteries has announced the remains of 11 more children are scheduled to be removed from the cemetery at Carlisle Barracks in September.