It's far more reaction than thought as he crosses the room in mere steps what it took her several strides to, closing both hands around her. He doesn't need to use both — she wouldn't be able to break his grip even if he'd only used one — but two feels safer. More secure. Less like she might vanish if he's unwise enough to let her continue. His grasp is unyielding, but not unsafe; he knows (has experience) just how fragile humans are and how much their bodies can take.

Later, he'll realize it was probably a poor impulse. That there were other just as effective methods he could have employed. He could have sat in front of the doorway, and made himself an immovable obstacle.

But in the moment, all he thinks is warning, warning and acts accordingly.

"Stop, please... you're not yourself..."