There are two species of white rhinos: southern and northern.
The southern [0] has one horn and there are an estimate of 20,400+ alive in the wild. Although they are still quite rare, they are considered the most common and widespread rhino.
The northern [1] white rhino is the one mentioned in this article and is much, much more rare. There are now only three individuals alive. I haven't found any confirmation, but I thought the northern was more popular by poachers because of the two large sized horns, instead of a large and small one from the southern rhino.
All in all, very sad we came to the point human beings have (almost, for now) killed yet another species.