Capturing happens in three stages:
Suppose the three players play the following (marked with white stripes) stones:
The first stage is placing all the moves on the board. Any connected set of stones of the same colour that contains one stone placed in this stage will be called “new”.
The board now looks like:
The second stage removes any connected sets of stones of the same colour that aren’t “new” and don’t have any liberties.
This would mean the A8 and A9 stones in the example, thus after the second stage it looks like:
The third stage removes any connected set of stones of the same colour that are new and don’t have any liberties, thus the board becomes like this:
