In the same sentence that Nephi uses to calm his brothers he terrifies Zoram. In that short space of time Zoram absorbs that the man beside him is not Laban, in spite of the armor and sword. He comprehends that the presence of Laban's armor and sword do not bode well for the well-being of Laban. He likely also understands that he has been an unwitting accomplice to what he must consider a major theft. It is no wonder that he "began to tremble, and was about to flee".