if someone punched you in the mouth for calling them an ugly name, the precursor to the punching incident would be when you called them the ugly name. one thing leads to another a lot of the time.
A precursor to an incident is something that happens before that incident and sometimes acts as an omen. For example, a precursor to colon cancer (sorry, it's the first thing that popped into my...
It is a incident that happened in rosewell where a so called 'flying saucer' landed or crashed. The legened is that it is a alian space ship that the government is keeping secret from the public.