That would have to be a massive margin call.

Looking over level 2 data and can't make sense of the trades. Prior day closing price vs this morning's opening 'ask' line up. What does NOT line up are the opening trades that caused the halt. In some cases you see a 25% delta between the 'ask' and the purchase price. Meaning, the opening trade executed successfully far, far below the 'ask'. Level 2 shows the trade time, trade price, market and lot size. So everything about the data appears to show a live trade but SEC is indicating data issue.

A live trade making it into the tape and market maker executing also lines up with the fact that all systems were go therefore automated systems caught the massive delta between closing price and opening trade. Since the delta was so large, automated halts triggered and trading stopped on those particular securities.

As a result you also see what appears to be multiple 'stop loss' orders also execute within the same second or next as the trade that caused the halt. Stop loss orders triggered and executed. So in essence, many investors were traded out of their positions without need. For those investors that were traded out unnecessarily, if not caught immediately and traded back in, may have lost on the upside depending if that position was up or down for the day.

Edit: Adding more info*

Another oddity. If you look at the the trade price that caused the halt you will also notice a few trades at a price higher than the offending trade but lower than the 'ask' that was in line with the previous close. So not only was their a "data issue" concerning the opening and offending trade, but more trades were also executed outside of what's to be expected given the 'ask' at the time.

I can think of two scenarios when this can happen.

1. Buy Limit order, set up by an investor to trade at a market price below a predetermined price and execute at the next available oppurtunity. Example: current price is $75 and investor sets up a trigger to buy at the next available price when security reaches $65. The security price reaches trigger of $65, order is triggered and finds a seller at $66. The trade is executed and investor now owns the security at $66.

2. Trades were executed outside of current channels without the knowledge of the market makers. Let's think this out. If market maker executes a trade in error at $65 when his book is clearly showing an 'ask' of $75, it wouldn't stand to reason that market maker would make several other error trades at $67, $68.50 and $71. Why? First because there isn't an 'ask' at those price points. Keep in mind the opening 'ask' was $75. So not only did the market maker error on the opening trade but continued to disregard or error on other phantom ask prices. Asks that didn't exist on the book. But where I'm leaning is that market maker had no clue the trades were happening and the trades that happened were intended to never have made it to the tape therefore never to have been made public. My guess is that this shit has been happening for a while but just now ran into a "technical issue". Technical issue for sure, they likely logged it into the wrong data stream.