The nun, more than ever convinced of the truth of what the children told  her, hastened to lay the facts before the priests. These discussed the matter among themselves and then, without awakening the suspicions of the children, proceeded also to question them.  They, in their turn, were deeply impressed and saw no reason for doubting what the children stated so firmly.

His Lordship the Bishop arrived in the course of the evening, and the priests gave him a full account of this consoling incident. He also wished to have first-hand evidence, and once more the children unwaveringly narrated to His Lordship all the facts as before. Inquiring into Michael's behavior, he learned that he was indeed a very good and innocent boy. He was cheerful and friendly, a good companion, a diligent student and, although he lived very far from the Church, he attended the instructions regularly and learned his lessons with unfailing care and diligence. The bishop, the priests and the nuns were convinced that Michael's Guardian Angel had indeed manifested his presence.

Source: Fr. Paul O'Sullivan, All about the Angels.