Wagstaffe said he arrived at his decision after reviewing police, fire and other first responder reports, the coroner's investigation and numerous videos of events at the scene. Ye, 16, was a Chinese student visiting the United States with classmates.
Wagstaffe said some of the videos show the girl on the ground outside the plane before the area is covered in foam. Other videos have shown Duckett's rig later driving over the same area after it was covered in firefighting foam.
San Francisco Fire Department Chief Joanne Hayes-White declined to discuss Ye's death other than to call it a "tragic accident."
Hayes-White said in a prepared statement that firefighters likely saved the lives of many critically wounded passengers scattered about the tarmac and still trapped aboard the Asiana Airlines flight that crashed landed July 6.
"If not for the professional rescue, triage, treatment and transport operations that were conducted by all involved agencies, it is likely that there would have been a greater loss of life," Hayes-White said.