The spell wasn't complete before the girl and her copies charged him, and he knew that he wouldn't be able to avoid all their attacks. Even if only one was solid, he wasn't in any state of mind to calmly reason it out, not with them already so close. Choosing one at random, he lunged forward, springing up to tear towards the face with his right hand. 

As the blow connected, he flinched a bit, almost as if he already regretted the decision. The girl he hit vanished, however, being only one of the clones.