Police released body camera video of the moment the shooting took place. They also released photos of the weapons they say were found inside the home.
Sacramento police called the shooting an ambush.
They say officers were attempting to retrieve items for a domestic violence victim out of the garage of the home. When officers learned the suspect had multiple weapons, they called for back-up.
Officers were attempting to make contact when the suspect opened fire with a high powered rifle, striking Officer O'Sullivan. She was transported to a hospital where she later died from her injuries.
A procession Friday brought her body from the coroner's office to a funeral home in Elk Grove. Fellow law enforcement and first-responders saluted and paid tribute.
Funeral plans have not been announced, but a vigil is planned for Sunday at Sacramento State.