It is just very unlikely and there is no explanation as to why the guy swerved and hit the other vehicle.
Because he (rightly) instinctively ducked from a loaded gun?
It happened to me under much lesser circumstances. I got uptight about snowballs falling over in my car on passenger side floor, and knee-jerk reached over to right them. Thus turning the wheel of my parents’ car and ramming it into the next parked car.