STORY: U.S. stocks ended lower on Thursday, with UnitedHealth Group down sharply and technology shares easing.

The Dow shed more than half a percent; the S&P 500 and Nasdaq each lost about two-tenths of a percent.

The declines come just one day after all three indexes notched record closing highs.

Patrick Kennedy, founding partner of All Source Investment Management, believes now is the time for stock market investors to take a bit of a breather.

"So, when it comes to market valuations, we think things look a little frothy right now, especially with, you know, the S&P trading at 23 times next year's numbers. [FLASH] There's still a lot of opportunity underneath the surface, in our opinion. We happen to like software, we like biotech and we like cybersecurity. Right now, those are the three big sectors we want to see our managers be exposed to. But other than that, at the index level, we think this is a good time to take a look at a pause."

Among individual movers, shares of UnitedHealth Group dropped more than 5% and were the biggest weight on the Dow and S&P 500. Shares of Cigna and Molina Healthcare also fell.

Health insurance companies are reassessing the risks for their top executives the day after the murder of UnitedHealthcare CEO Brian Thompson in Manhattan. UnitedHealthcare is part of UnitedHealth Group.

Shares of Synopsys fell more than 12% after the chip design software firm forecast fiscal 2025 revenue below Wall Street expectations, in part due to a slump in China sales.

And cryptocurrency and blockchain-related stocks lost steam after bitcoin fell below the $100,000 level after eclipsing it for the first time ever earlier in the day.

MicroStrategy, the largest corporate holder of bitcoin, ended down nearly 5%.

Investors now turn their attention to Friday's monthly nonfarm payrolls report for clues on the Federal Reserve's next policy moves.