Mello was an incredibly smart yet emotional orphan from Wammy's House.
Retrieved March 17, 2014.
I DON'T WANNA DIEEE!!!! The movie at least features a throwaway line about him being a superb marksman.
On the one hand, he makes it very clear that he doesn't care whether Light wins or loses, and almost never helps him unless there's something in it for him.
We were safe at the orphanage, but we'll never be safe out here.
This, of course, gives her enough leeway to hide pieces of Death Note and a writing utensil.