Claire Davis: Arapahoe High School Colorado shooting victim dies at hospital

(CNN) -- Claire Davis, the 17-year-old high school senior shot Dec. 13 by a classmate at their Colorado school, died Saturday at the hospital where she was being treated.

"It is with heavy hearts that we share that at 4:29 p.m. this afternoon, Claire Davis passed away, with her family at her side," Littleton Adventist Hospital said in a statement.

"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."

According to police accounts, Karl Pierson, 18, walked into Arapahoe High School armed with a pump-action shotgun, a machete and a backpack containing three Molotov cocktails, a bandolier of ammunition across his chest.

He shot Davis once in the head and fired randomly into school hallways. Police said Pierson was looking for revenge against a librarian, but couldn't find the faculty member and killed himself as a school resource officer closed in.

Davis did not know the shooter and was just a random victim, police surmised. She had been in a coma since the shooting.

"We cannot begin to understand why Karl did what he did," the shooter's parents, Barbara and Mark Pierson, said last week in a statement. They also offered prayers "for the entire Arapahoe High School community, as we know your lives are forever changed by this horrific event."

Hundreds of people attended a vigil for Davis last Saturday.

Davis was described as a sweet girl who loved horses and the English boy band One Direction.

After friends started a Twitter campaign, the band recorded a 13-second video message and sent it directly to the Davis family, a source close to One Direction told CNN on Thursday.

The video shows singer Liam Payne delivering the message as the other four members stand by.

The shooting happened about 10 miles from where Eric Harris and Dylan Klebold killed 12 students and one teacher in a rampage at Columbine High School in April 1999 before killing themselves.