Still they would get low odds and the risk/reward ratio makes that a terrible bet since it would only take one accident to lose all your money. For like a 1% return.
if you think the odds of something happening are lower than the share price, you sell / short / buy "no". if you think they are more likely, you buy. the odds are 100% if you plan on killing someone, and surely some people will think its less than 100%. they will buy "no" shares because they think that its less than a certainty that someone is going to be assassinated.