Six Million Players Come Back 4 Blood

This tweet reveals that Back 4 Blood has now been played by more than six million players since the launch of Turtle Rock Studios' co-op zombie shooter (thanks Wccftech). The milestone is noted in an animated gif with this caption:
Thanks for all your hard work, Cleaners! With this many Cleaners on our side, we'll stop the Ridden in no time. #Back4Blood