There is a huge difference between short-selling stock in a public company or offering privately held stock when you are not an officer. selling stock of a company that you are C-level exec of (or founder) and that you hit with 'bad news' during a fundraising round is not going to make you any friends.
Your co-shareholders could easily make a claim, whether it will stick or not is as always up to a judge but it's very dangerous territory, and you are likely operating outside your shareholder agreement (at least, all the ones that I've seen) and also likely outside of your mandate as an officer of the company (depends on your role, but usually you would be). These things have to be handled with some diplomacy and tact otherwise you could very well harm the company directly in such a way that the harm would be easy to quantify. Which is a very bad situation to be in, so make sure you play by the book when doing these things.
Not sure about the US and not a lawyer, but often as a founder/board member you sign a shareholder agreement which includes a provision not to undertake anything which would deliberately cause damage to the company/other shareholders. There are perhaps other points as well. I imagine the US is more litigious here than Europe (where my experience comes from)
