"We believe it's her," Sheriff Shannon Moon said about the somber discovery made by a group of volunteer divers that searched for the 16-year-old in the Prosser Creek Reservoir near Truckee on Sunday.
Authorities confirmed that the car pulled from the reservoir was Kiely's, but they stopped short of saying the body inside the car is definitely Kiely.
Her family released a statement on Monday afternoon thanking law enforcement, the community, and friends for their help in the search for Kiely.
"We have weathered a storm of unfathomable force, and it is purely thanks to the army of warriors, matriarchs, healers, and helpers holding us up that we continue to stand today," they said.
They continued, "While we accept this sadness cast under death’s shadow, the rising sun shines light upon us, reminding us not to mourn our loss, but to celebrate Kiely’s spirit and the gift that we all received in knowing her. Kiely will surely remain with us even though we will not get her back."
Kiely was last seen at a large party on August 6 at a nearby campground.
A volunteer team called Adventures with Purpose announced they had found Kiely's missing Honda CRV with a person inside the vehicle. Law enforcement dive teams had previously searched the reservoir as well, raising questions about why they had not spotted the Honda.
An autopsy will be conducted Tuesday to determine the cause of death. Toxicology tests will take weeks to yield results.
The search for Kiely had expanded to include multiple agencies, such as the FBI.Soon after she vanished, the Placer County sheriff's office said they were treating the case as a possible abduction.
Last week, authorities revealed they made a sweep of registered sex offenders as their investigation into her whereabouts continued.
Although there were hundreds of young people at the party that Kiely attended, the sheriff's office said last week that they'd found many potential witnesses had not come forward, perhaps because they feared getting in trouble for underage drinking.
Kiely had texted her mother to say she was leaving the party, but she never made it home. Her cellphone last pinged at the campground on August 6.