Claire Davis had been on life support ever since she was shot by Karl Pierson, 18, who shot and killed himself after setting a fire with a firebomb in the school library.
Arapahoe County Sheriff Grayson Robinson said Pierson was armed with a 12-gauge pump shotgun, three Molotov cocktails and a machete when he entered the school looking for his debate coach. He also had 125 rounds of ammunition on two bandoleers.
Littleton Adventist Hospital announced Davis' death in a Facebook post Saturday afternoon, the Denver Post reported.
"Despite the best efforts of our physicians and nursing staff, and Claire's fighting spirit, her injuries were too severe and the most advanced medical treatments could not prevent this tragic loss of life," the announcement said. "Claire's death is immensely heartbreaking for our entire community, our staff and our families."
Investigators think Davis was randomly targeted, the Post reported. She knew Pierson but they were not friends, officials said.
Members of Congress to keep receiving porn magazine
Rosie O'Donnell unveils nearly 50-pound weight loss