What do Montag's hands do? And what is he afraid they will do?

Montag's hands were grabbing the woman's books. Montag's hand took a book, which he crushed to his chest. Montag is afraid his hands will make him a thief.

Montag's hand closed like a mouth, crushed the book with wild devotion, with an insanity of mindlessness to his chest. The men above were hurling shovelfuls of magazines into the dusty air. They fell like slaughtered birds and the woman stood below, like a small girl, among the bodies. Montag had done nothing. His hand had done it all, his hand, with a brain of its own, with a conscience and a curiosity in each trembling finger, had turned thief.. Now, it plunged the book back under his arm, pressed it tight to sweating armpit, rushed out empty, with a magician's flourish! Look here! Innocent! Look!