Joe Catron, a human rights activist who witnessed the shooting and documented the incident in photographs posted on Flickr, said in a telephone interview from Gaza that, although it seemed certain the young man would die without emergency medical treatment, the rest of the small party with which he was traveling had no choice but to retreat when shelling resumed in the area after the filming had stopped. The two people closest to the gunshot victim were convinced that he was dead by the time they left, Mr. Catron said.