By the way, why everyone point out that Blackbeard killed Whitebeard? What had he done? Just pinned him with some pesky bullets that doubtly made it past first skin layers? Whitebeard died from age, illness and all those monstrous wounds that would instantly destroy an ordinary man. After getting stabbed around heart, getting a lava punch into the chest and having half of his face blown away he was still standing. And some shitty peas killed him? No. I insist that he died and was not killed.
You're technically right, Whitebeard was killed by Squad, the marines and BB pirates.
But BB pirates were the ones who gave him the final "blow", so they've killed him.