That would be a dumb move on his part. Stock manipulation that blatant would have the SEC chewing on his entrails in a matter of minutes.

The most likely scenario is that he was paid at least partially in company stock. This is fairly common for the C-level, because it allows them to loosely tie their income to the company’s stock price. When the company does well, the C-level makes more money.

So he likely had an automated recurring sale set up, to sell off part of what he was being paid. So if he’s paid 25 stocks per pay period, maybe he sells off 15 automatically and keeps 10. This allows him to remain more liquid (or diversify his investment portfolio by reinvesting that money into other companies’ stock,) so he isn’t keeping all of his eggs in one basket. It’s the smart thing to do, but can also be bad PR if the stock for your company tanks right after your automated sale goes through.

At most, he could’ve timed the announcement to happen right after his stock sale. So he can automatically sell when the price is still good, then watch it tank immediately after the sale. That’s not stock market manipulation per the current rules, (because he didn’t actually change how much he was selling, or change when the sale would happen) but it’s still scummy.