One very real explanation that I don't know if it's been mentioned or not yet, is that someone had a stop loss order in at 3.55 price (or whatever it was) and the mm decided, for whatever reason to take it out and then very quickly move it right back up. My understanding is they have all kinds of flexibility in the role as a market maker.
You got me thinking about that other totally outrageous trade awhile back, when on the move to 11.00+, our chief scientist got a execution of something like 2 million shares at/near top, as I recall, only to see it very quickly and dramatically fall in share price. An opposite, but very similar event it seems?