At this point, Papyrus has lost all the belief and faith that he had that humans could be good, and is now out to get revenge for the death of his brother, and friends. Instead of meeting Sans in the Last Corridor, you meet Papyrus, and the events from this time on lead up to his fight with you. He stops Papyrus from fighting you in Snowdin, and tries to fight you himself, but dies, leaving Papyrus to watch all of his friends die with his own eyes. After you, the protagonistrepeatedly play through a Genocide Route, Sans tires of watching Papyrus, and his friends die, so he finally decides to interfere.
