Emotions can get in the way of truth-seeking. People do not process information in a neutral way.

Terrible events produce outrage, and when people are outraged, they are all the more likely to accept rumors that justify their emotional states, and also to attribute those events to intentional action.

...when like-minded people get together, they often end up thinking a more extreme version of what they thought before they started to talk to one another.

Some rumors simultaneously relieve "a primary emotional urge" and offer an explanation, to those who accept them, of why they feel as they do; the rumor "rationalizes while it relieves.