YAHOO [BRIEFING.COM]: Equities sold off steadily throughout today's session, and the S&P 500 ended lower by 2.3%.

The major averages were pressured from the opening bell as global growth concerns returned to the forefront. In China, first quarter GDP rose 7.7%, which was below the expected growth of 8.0%. The disappointing report added to the weakness of the commodity complex, which saw an extension of last week's selling.

The key indices were hovering near their lows when reports indicated two explosions took place at the finish line of the Boston Marathon. Sellers reacted to the news by pushing equities to fresh lows.

Two of Friday's biggest laggards also ended today's session leading to the downside. Energy and materials both fell nearly 4.0%. A 3.3% drop in crude oil contributed to the weakness of the energy sector while producers of basic materials lagged across the board.

Gold miners endured yet another rough session as the Market Vectors Gold Miners ETF (GDX 29.02, -3.20) fell 9.9% on the heels of a 9.5% plunge in gold to $1356.80. Meanwhile, silver tumbled 13.0% to $22.90. Including Friday's decline, gold has suffered its largest two-day drop in about 30 years.

In addition to precious metals, copper fell 2.1% to levels not seen since June of last year. Similarly, steel producers saw significant weakness as the Market Vectors Steel ETF (SLX 40.23, -2.02) lost 4.8%. As a result, the steel ETF is now sitting at a nine-month low.

Today's selling did not spare the two groups which have led the bulk of the first quarter market rally.

The Dow Jones Transportation Average sank 3.8% as all 20 components settled firmly lower. Late-afternoon trade saw airlines fall to their lows following the worrisome headlines out of Boston. Delta Air Lines (DAL 14.91, -0.57) dropped 3.7% while JetBlue Airways (JBLU 6.73, -0.47) settled lower by 6.5%.

Elsewhere, homebuilders underperformed broadly as the disappointing April NAHB Housing Market Index contributed to the weakness. Toll Brothers (TOL 30.50, -2.54) lost 7.7% while the broader SPDR S&P Homebuilders ETF (XHB 28.17, -1.47) tumbled 5.0%.

With equities ending firmly lower, the CBOE Volatility Index (VIX 16.61, +4.55) jumped over 35.0%, settling at its highest level since late February.

No group was able to escape today's selling. Small cap stocks underperformed the broader market as the Russell 2000 lost 3.8%.

Today's volume was well-above average as nearly one billion shares changed hands on the floor of the New York Stock Exchange. Today's tally marked the highest total since February 28th.

While Chinese economic data missed expectations, domestic economic news did little to paint an upbeat picture. The Empire Manufacturing Survey for April registered a reading of 3.1, which was down from the prior month's reading of 9.2. Economists polled by Briefing.com had expected that the survey would slip to 5.0.

Meanwhile, the April NAHB Housing Market Index registered a reading of 42, which was lower from the prior month's reading of 44. Today's reading fell also short of the Briefing.com consensus which called for a reading of 45.

Tomorrow, March CPI, core CPI, housing starts, and building permits will all be reported at 8:30 ET. In addition, March industrial production and capacity utilization will both be announced at 9:15 ET. On the earnings front, Coca-Cola (KO 40.09, -0.99) and Goldman Sachs (GS 146.46, -2.66) are scheduled to report their quarterly results prior to the opening bell.DJ30 -265.86 NASDAQ -78.46 SP500 -36.49 NASDAQ Adv/Vol/Dec 279/1.74 bln/2246 NYSE Adv/Vol/Dec 377/975.7 mln/2702

3:30 pm :

• May crude oil fell back below $90 per barrel and to a new low this year of $87.86 per barrel as weak Chinese GDP data and broad market weakness put pressure on prices. The energy component pulled-back from its session high of $89.75 per barrel and settled with a 2.8% loss at $88.74 per barrel.
• May natural gas touched a session high of $4.25 per MMBtu in early floor trade but retreated into negative territory in mid-morning action. It dipped to a session low of $4.12 per MMBtu and settled at $4.14 per MMBtu, or 2.1% lower.
• June gold extended last session's losses as continued selling pressure, broad-based weakness in commodities and disappointing Chinese GDP data pressured prices. The yellow metal tanked to $1355.30 per ounce in mid-morning action, setting a new low since October 2010. It settled at $1361.20 per ounce with a 9.3% loss.
• May silver also tumbled to levels not seen since October 2010. Prices fell as low as $22.94 per ounce before consolidating slightly above that level and settling with an 11.2% loss at $23.35 per ounce.