At 00:31:06 one single shot hits the tree.
And then, as announced, they all show up carrying shotguns!
Shotguns, as shown, fire buckshot, not single slugs
A shotgun's single slug is called "Brennecke" and would have done a lot of damage to the tree.
Absolutely and totally unrealistic shooting.
A shotgun shot would have rained tens of pellets on Alex's face.
When Fiona exits the swimming pool the path she walks across the tile floor is already wet from a previous take.