Twelve American tourists in their 60s and 70s were killed this week when their tour bus careened off a 300-foot cliff in the Andes mountains. The victims were passengers on a Celebrity cruise liner who had taken an independent excursion into a wilderness park, 90 miles inland. Chilean prosecutors said the driver may have fallen asleep at the wheel. Ten of the dead were friends from a New Jersey retirement community. "It says something about who they were that they died in the mountains of Chile," said Phyllis Magier, who runs the retirement community. "They died in the process of living."