It isn't exactly celebrating suicide, it's kinda making fun of it in a way.

It started from some myspace post long long ago, in which some kid named Mitchell had killed himself and one of their friends or family members made a memorial myspace page about it including the typo "He was such an hero, to take it all away." The post continues to use "an hero" multiple times, (h/o I bet I can find it, brb.)

/b/tards latched onto it pretty quick, and the meme became that people who killed themselves are "an hero" just like Mitchell.

Edit: Yup, found it. Thanks knowyourmeme.

"He was such an hero, to take it all away. We miss him so, That you should know, And we honor him this day. He was an hero, to take that shot, to leave us all behind. God do we wish we could take it back, And now he's on our minds. Mitchell was an hero, to leave us feeling like this, Our minds are rubber, our joints don't work, Our tears fall into abyss. He was an hero, to take that shot, In life it wasn't his task, He shouldn't have had to go that way, before an decade'd past. Now he sits there in my heart, this hero of mine, Always there to make me smile, Make me feel just fine. He had courage,that boy did, courage in his heart. To take that shot, To end his pain, To tear us all apart. But in the end, he died in courage. Lacking, nevermore, He died a hero, Mitchell did, And we'll love him forevermore. We love you like an brother. We miss you so much. We will always love you, kid. Rest In Peace Mitch. ~Lila"