When Xavier is pushed down the stairs you see him drop the gun on the stairs and see his hand is clearly empty, in the next shot you see the gun in his hand with no possible way of him getting up and getting it.
When she tries to escape in his Ford truck he says it did not start as has a manual choke. The truck is not old enough to have a manual choke.
They say they are at the lighthouse in Caribou, but Caribou is not only not on the water but it doesn't have a lighthouse. And it is approximately five hours away from Biddeford which is where her Bed & Breakfast is alleged to be.