How did Bluestar die?

Bluestar died saving Fireheart/star from the dog pack and fell in the gorge, that is where she drowned and Fireheart was able to surface her to the shore, but after 3-5 मिनटों she died, Tigerstar tried to kill her sooner but Graystripe stopped him..... Bluestar's death was so sad :'(