Claire Davis, 17, died Saturday afternoon around 4:29 p.m., according to a statement released by Littleton Adventist Hospital.
"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. Claire's death is immensely heartbreaking for our entire community, our staff and our families," the statement read.
On Friday, Dec. 13, Karl Pierson, 18, walked through the north entrance of his school with a shotgun, three Molotov cocktails, a machete and more than 125 rounds of ammunition.
He immediately opened fire randomly inside the school, shooting Davis in the head at point-blank range while she was sitting near the library. The 17-year-old had remained hospitalized in critical condition until Saturday, when she passed away.
Pierson's motive is believed to be revenge against the debate team instructor, who was also the school's librarian, after he was kicked off the team. The librarian escaped, and Pierson killed himself in the library 80 seconds after entering the school.
Friends and well-wishers had been posting prayers online and raising money to help pay for her medical care.
"The Davis family would like to thank everyone who have sent their best wishes and prayers, and are grateful for the kindness and support of the community. They know that you all are mourning with them, and again request privacy during this time of grief," the statement read.
ABC News and The Associated Press contributed to this report.
