Board Thread:General Discussion/@comment-30630533-20171231150337/@comment-33621103-20180101045047

Peter Pan was stabbed with a magic dagger. You use a magical weapon to kill a magical being.

Rumple sacrified himself because Pan stated that he can't die unless Rumple also dies. The show never elaborated further on this - one of many loose threads on the show.

When Peter Pan's soul went into the Underworld, Rumple "killed"/trapped Pan by using water from the River of Lost Souls.