I'm about halfway done with it.

If the gun user is highly trained or a random punk it would greatly change how likely they could hit a moving target and at what range. If the later I could logically see them missing someone skilled at dodging enough for them to close the distance. If a trained soldier is in the room, even with only a pistol, the odds would make it where I think they could shoot that person down without much difficulty unless they had plenty of good cover.