What does "flushed to guns" mean?

The hunt continues until either the fox evades the hounds, goes to ground (that is takes refuge in a burrow or den) or is overtaken and usually killed by the hounds. In the case of Scottish hill packs or the gun packs of Wales and upland areas of England, the fox is flushed to guns. Foxhound packs in the Cumbrian fells and other upland areas are followed by supporters on foot rather than on horseback. In the UK, where the fox goes to ground, terriers may be entered into the earth to locate the fox so that it can be dug down to and shot.

Source: https://en.wikipedia.org/wiki/Fox_hunting

I thought the same article mentioned that the humans are unarmed. Isn’t it the dogs that do all the killing, if any killing takes place at all? What’s this with guns? And "flushed with" guns? What does that mean?