The benchmark S&P 500 index reached its highest level in more than four years yesterday, reports Financial Times.

It hit 1,426.68, its highest intraday rise since 2008. The jump surprised investors, as trading volume is traditionally light during the summer, and very few sessions have seen major moves this month.

The rise was driven by gains in three sectors: energy, technology and financial. The index has climbed 10.5% since June.

But, stocks did fall shortly after the S&P peaked. The index faced technical resistance, and traders were also busy cashing in their gains, says Reuters.

Jim Paulsen, of Wells Capital Management in Minneapolis, told Reuters, “It’s not uncommon you run into some resistance at new highs.”