Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Investors in postsecondary education provider Bridgepoint Education (NYSE: BPI) had a rude awakening this morning when shares fell 12% to start the week.

So what: When a big shareholder decides to sell, the market doesn't usually respond positively. When an investor holding 65% of a company's shares decides to sell, a big slide is coming. That's exactly what happened today after Warburg Pincus said it was looking to sell all of its 34.6 million shares in the company.

Now what: It's hard to blame Warburg Pincus for taking the huge profit it is sitting on in Bridgepoint Education. The private equity firm has been an investor in the company since 2004 and its stake is up more than threefold since the company went public in 2009. This may be a big hit for investors today, but private equity investors have to cash out eventually, so I wouldn't read into it too much. With a P/E ratio of just 10, shares look to be priced right, and this could be a great buying opportunity for long-term investors.

Interested in more info on Bridgepoint Education? Add it to your watchlist.

Fool contributor Travis Hoium does not have a position in any company mentioned. You can follow Travis on Twitter at @FlushDrawFool, check out his personal stock holdings or follow his CAPS picks at TMFFlushDraw.

The Motley Fool owns shares of Bridgepoint Education. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.