How did the brontosaurus die?

A massive meteore hit the earth to cause the extinction of all the dinosaurs including tyrannosaurus rex. No one has proven anything, but the meterite theory has pretty much been cancelled out of the plausibly theories. It is more likely that they evolved and formed birds or that the weather change caused them to die. Since someone redirected the question "How much does a Tyrannosaurus weigh" to this question, I will answer it here: Up to 6.8 metric tons (7.5 short tons).