How did the angels of mercy and the angels of punishment dispute over the matter of the man who killed ninety-nine souls, even though they are commanded by Allah and do not choose or judge?

The angels are honored servants who do not disobey Allah. They have been entrusted with duties: angels of mercy are for seizing the souls of believers, and angels of torment are for seizing the souls of disbelievers. Angels do not know of the unseen except what Allah has taught them. Therefore, their understanding concerning human beings differs, and they dispute until Allah judges between them. The dispute between the angels of mercy and the angels of torment at the time of death of the man who repented was only in obedience to Allah's command and in fulfillment of what they were entrusted with.