Mary doesn't shoot Sherlock, she tries to knock him out.

However, Sherlock is a lot more resilient than she expects, and manages to not only catch her wrist and avoid her blow, but wrestle the gun from her hands.

Now it's Sherlock pointing the gun at a very surprised and probably very frightened Mary, with Mangussen kneeling in the background watching eagerly, and John on his way upstairs.

What happens next?