Board Thread:Character Discussion/@comment-25823557-20151207112428/@comment-25733960-20151212144057

This is explained in a deleted scene:

https://www.facebook.com/OnceUponASpoiler/photos/a.928723963828466.1073743065.528035687230631/1079805902053604/?type=3&theater

So basically, he would had killed himself to go the Underworld and help them