After being left for dead less than a year ago, GameStop (GME -2.64%) has come roaring back, ending the day up 50% to a new all-time high of $65.01, after trading for roughly $2.50 per share early last year. At one point on Friday, shares had gained as much as 78%, before tripping Wall Street breakers that temporarily halted trading.

The recent run-up has all the earmarks of a short squeeze, which accelerated this week when a spat broke out between noted short-seller Citron Research and a group of investors that frequent the r/WallStreetBets subreddit. Members of the forum remained bullish and even encouraged other retail traders to buy GameStop. 

A graph arrow climbing steadily with a $100 bill as a backdrop.

Image source: Getty Images.

Citron editor Andrew Left threw in the towel Friday, posting from a temporary Twitter account, "We will no longer be commenting on GameStop, not because we do not believe our investment thesis but rather the angry mob who owns this stock." He went on to allege that a number of crimes had been committed and saying his family had been "terrorized." He had previously alleged that Citron's original Twitter account had been hacked.  

Left had promised a livestream event earlier in the week in which he would reveal five reasons GameStop was going to $20, saying that those buying the stock were "suckers." After postponing the event Wednesday, it was abruptly canceled on Thursday and replaced with a video posted to Twitter and Alphabet's YouTube. The video was widely reviled, with a number of Twitter users citing factual errors and rehashed reasoning.

While trading volume was already high yesterday, it shot through the roof today, a clear sign that the short squeeze was gaining traction. While 55 million shares of GameStop traded hands yesterday, that soared to nearly 196 million today, 17 times that average volume during the month of December.