Remember last week when the Dow went nuts and dropped almost 1000 points?

Reuters is reporting the myserty is solved and if true, is almost worse than the speculations. It was a hedge fund, money manager Waddell & Reed Financial Inc., selling e-mini contracts. They run a $22.1 billion fund.

Waddell on May 6 sold a large order of e-mini contracts during a 20-minute span in which U.S. equities markets plunged, briefly wiping out nearly $1 trillion in market capital, the internal document from Chicago Mercantile Exchange parent CME Group Inc said.

The e-minis are one of the most liquid futures contracts in the world, providing holders exposure to the benchmark Standard & Poor's 500 Index. The contracts can act as a directional indicator for the underlying stock index.

Regulators and exchange officials quickly focused on Waddell's sale of 75,000 e-mini contracts, which the document said "superficially appeared to be anomalous activity."

More than a week after the incident, it was still not clear what impact the unusual trading in the futures contracts had on the broader meltdown in the stock market.

It seems he sold 75,000 of these contracts when the average is about 50,000 in one hour.

Here is the definition of an e-mini futures contract.