Is a bear market showing up? Certainly, some qualities of a bear have started to arrive.

The action last week on April 24 might have indicated that we're ready to shift gears. We saw a downright nasty reversal that day, with higher volume levels and some very heavy selling.

Further, there was little buying of protection, which is often seen as a trait of bull markets. (Bear markets arrive unannounced.)

Now, some of the biggest rallies occur during bear markets, but few traders or investors are nimble or efficient enough to play the downside and profit well from them. Both bulls and bears usually lose money in bear markets. That's just a fact.

Of course, big institutions use bear markets to buy stocks for the long haul. After all, pensions, banks, hedge funds, trusts and foreign entities aren't your day-trader type.

They buy stocks and hold them for years, letting shares appreciate and pay dividends if that's the case. However, when interest rates rise and risk changes (as we might be seeing now), the argument for holding stocks can change, too.

Now, we're already seeing rising volatility, which is normal during at least a bull market's correction phase. Big money will buy heavy pieces of volatility or index puts and hold them short term to weather the storm. That's a cheap way to buy protection without having to sell long-term holdings.

But we saw something quite different as well last week. Stock sellers were quite active, but buyers of volatility were noticeably absent. Stalwart names like Caterpillar (CAT - Get Report) , Alphabet (GOOG - Get Report) , (GOOGL - Get Report) , Lockheed Martin (LMT - Get Report) and Boeing (BA - Get Report) all sold off heavily as dip buyers stood back to wait. That's classic bear-market activity.

Buyers haven't been rushing in to buy stocks like Caterpillar on a dip.
Buyers haven't been rushing in to buy stocks like Caterpillar on a dip.

Now, I'm not saying we're in a bear market for sure, but the weight of evidence is certainly piling up in the bears' corner. Big institutional money is starting to get nervous with each pull down toward the S&P 500's 200-day moving average, for good reason.

After all, the S&P 500's 200 DMA has more or less held firm for several years. The last real test came in early 2016, but the S&P 500 has risen some 25% since crossing back over that line.

The Bottom Line

The market's price action since late January hasn't been inspiring, and with bond yields up, commodity prices higher and sharp price moves among equities, it might be time to break out the bear suit.

I'm willing to continue giving this long bull market the benefit of the doubt, but the evidence that it will continue to run is looking increasingly thin.

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(This column originally appeared Monday on Real Money, our premium site for active traders. Click here to get great columns like this from Bruce Kamich, Jim Cramer and other writers even earlier in the trading day.)

At the time of publication, Lang was long CAT, GOOGL and LMT, although positions may change at any time.