Less than a month ago, high-stakes poker pro Tom Dwan Tweeted that he had just experienced his “biggest loss ever” at a poker table. For him, that’s a big deal.

In taiwan for the 1st time ever… Not leaving the airport tho. Maybe next trip. Had my biggest loss ever yesterday — Tom Dwan (@TomDwan) September 24, 2013

Card Player spoke to a person who said he was watching the game in question at StarWorld Casino in Macau when all the madness went down.

According to the person, the game was shorthanded and Dwan had been playing nearly 24 hours straight. He eventually was felted at around 5 a.m. local time.

Dwan walked out of the casino down more than $4 million.

It’s unclear what stakes were being played, as well as what the buy-in was, but the source said that for at least three straight hours every single pot was at least (approximately) $40,000.

Obviously many grew to be much, much larger.

The loss for Dwan was about double his worst ever tracked online session.

High-stakes poker action these days has found a home in the former Portuguese colony, the only place in China where gambling is legal. Wealthy high rollers from mainland China have not only made Macau the largest gambling market in the world (around $40 billion annually) but also the hotbed for earth-shattering Texas hold’em pots.

Despite Las Vegas not being home to the largest cash games in the world anymore, some of the Macau poker regulars make the trip if the stakes are right.

In 2012, the WSOP held a $1 million buy-in that attracted such customers. That event will return in 2014 and should once again bring in some poker players who typically stay in Macau to play cards. The cash games at Bellagio or Aria could also be monstrous during that stretch.