The three Purifiers hadn't been prepared for stumbling bookcases. They weren't sure if they were a mutie transformed or just being manipulated. That hesitation lead them to getting boxed in by lightweight bookcases. So they knocked the books off the bookcases and started firing their guns through the provided book fort. They sprayed bullets all over the library except where the fourth Purifier in the room managed to avoid the bookcase trap.

The fourth Purifier in the room managed to get out of the way of the way of the bookcase enclosure. He waited for the others to finish. He'd rather not get shot up.