Mr. White....maybe? It is debatable.
Could have been Mr. Pink. Afterall, he was shot during the "Mexican standoff".
It was Joe that raised his gun to Mr. White, then Mr. White returned the favor to Joe and Eddie then raised his gun to Mr. White. Mr. Pink was there,
just not shown. He took fire so I would assume he returned it. The logical explanation would be that Eddie changed his line of fire to Mr. Pink, as
Joe was focused on Mr. White, who was focused on Joe.
Or, Mr. White killed Eddie and Joe, and then Mr. Orange after he had revealed his true identity. Mr. Pink just got caught in the crossfire.
I'm going with theory #1, Mr. Pink.
en.wikipedia.org... 
