Edit to add: feel free to email me (address is in my profile) if you'd like to discuss this with someone in private. I've co-founded multiple startups, but don't have any experience with a bad situation like this, so could give general perspective only, but if you just need someone to talk to I can be that person.
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The first question to ask is, what would you like to see happen?
Considering the short runway and the apparent problems with the CEO, do you see value in the company and would you like to keep it alive? Are you ready to write it off, and you just want to manage the endgame to ensure that yourselves, other employees (if any), customers (if any), investors, or other parties are treated fairly? Is there some other outcome that you'd like to optimize for?
Separately: who are the members of your board? I've never dealt with a situation like you're describing, but at a high level I imagine you have basically three channels for action:
1. Call a board meeting, fire the CEO.
2. Legal action. I'm not sure whether this sort of action is something you could sue over, something you could ask the police to press criminal charges for, both, or something else. Consider, however, that filing a lawsuit is expensive, and it's not obvious to me that either of these actions would benefit you in any practical way (aside from revenge, if you're looking for that).
3. "Soft power" – threaten to do (1) or (2) above, or to quit, or do other things, in order to coerce the CEO into leaving / behaving better / whatever else you'd like to see.
One other note: while I'm off the edge of my experience and expertise here, I can imagine possible scenarios where you could wind up in legal trouble if you're not careful. (For instance, if you're on the board and fail to take appropriate action now that you're aware of the problem?) You might want to consult a lawyer for this reason alone.
