I once read about this in a book on mass psychology. Statistically, a well-publicized death or deaths (aircraft or auto accident, murder, suicide, mass cult suicide, whatever) will strengthen the urges for suicide and murder. Researchers have noticed a frightening spike in the number of suicides and bizarre accidents about a month after the original event.

Furthermore, the type of deaths match. For example, after an aircraft accident--where many die at the hands of one or two--there are a suspicious number of auto accidents where the driver simply steered a carload full of people into a tree. However, if the original incident was a single suicide, there are a great number of auto accidents where a lone driver steers the car into a tree. This is really quite scary.