The family of Caitlyn Gonzales told ABC7 News that she died from complications from pneumonia.
"She liked to make everyone smile and there was never once where I ever saw her down," said one student.
Grief counselors have been available all week for students and staff at Liberty High.
Liberty High School in Brentwood grieving after fourth unrelated student death this year. pic.twitter.com/HXpG9slGg8— Cbarnard (@CornellBarnard) February 2, 2018
As a precaution, officials say the school was disinfected by the Contra Costa County Health Department.
Even more shocking, it's the fourth Liberty student to die this school year from unrelated causes. In January, a student died by suicide. The cause of two other deaths are unknown but not related to the flu.
"The thing I've been impressed with the most is the level of caring and compassion by this entire school community," said Liberty Union High School District Superintendent Eric Volta.
Some students say everyone is helping each other.
"Some people have been talking about it, helping other people out but it's tough times but we'll get through it," said student Damien Taylor.
"Right now, as parents, we're just making sure that we speak with our kids and just educate them and let them know what's going on and definitely to pray for their friends," parent Shelley Taylor said.
And prayers for a high school community dealing with so much loss.