[molson]

I've watched too many Youtube videos breaking down that scene, and once you understand the screen language of David Chase, it does become pretty obvious he was killed.

The remaining mystery was/is who killed him, and there's quite a number of well-supported theories on that too. I think a lot of different hints were dropped implicating several people in being part of it. Most simply though, Butch just continued the plan that had been in place - decapitate New Jersey, including the boss, and absorb whoever was left and willing to take orders from them - and by then, they knew who that would be. (Certainly Patsy, and, more debatably, and there's a fun Youtube video making this argument, Paulie.) Butch was in a great position by the end. He didn't betray Phil, so nobody would hold that against him, and he was able to lure Tony out into the open, which nobody still alive who mattered by the end would hold against him.