His shadow fought back, breaking equipment, injuring the researchers, and guard personnel. However, without William the shadow could not exert a fraction of its power.
It needed a conduit to exert its full power, that was William. The shadow also doubled William's already monstrous power.
William could not get to his shadow unless he broke into the compound, but he would need more power and a plan to get in and out safely.
He set out back to the academy, he could do nothing now, he could not break into the compound with the equipment on him, and as much as he did not like it, he was not bullet proof, even more so with how powerful the guns the compound had.
...
He needed more safeguards. He was sure he could break the door, but he would not do that yet, it would be short-sighted. He needed to be certain he could win before he broke down the door and opened that can of worms.