Even if the gun is against the fox when the brain tells the trigger-finger to fire, that doesn't mean it's still going to be there when the gun does fire.
As for "don't shoot", I'm not sure what alternative course of action would rate to be better. I don't think the fox was going to leave on its own, and if not stopped it could have continued to do more damage. So either do nothing for a few minutes, or else try to stop the fox some other way. But with what? The "lock time" for a rifle is a lot shorter than the lock time for a blunt-object weapon. So swing at the fox with a baseball bat and maybe hit the woman? That seems brilliant.
Doesn't even mean the bullet is going to go when you aim it. .22s that hit bone are famous for bouncing around and heading off in unexpected directions.
Swinging sideways would be a dumb thing to do. What you would want to do is swing down across the backbone either breaking it or stunning the animal so badly it breaks off the attack and you can quickly deliver follow up blows. Worst case when swinging down is you miss the fox and graze wifeys leg or hit her foot...and then the fox attacks you before you can recover. Although, it seems that when psycho, they have a tunnel vision that tends to keep them locked onto their original victim
If you're lucky, you have one of those weed rakes with the five long sharp tines, a hoe with weed prongs on the reverse side or, a pitchfork. Once you get a tine or two in him, the battle has sort of shifted decidedly in your favor.