Authorities say they believe a body found in a grave is a San Diego County teen who formerly lived outside Chicago and who went missing last week.
King's parents, Brent and Kelly King, have been informed, Gore said, adding that they're "devastated."
The likelihood that the body was King's led thousands to gather for a somber candlelight vigil in her memory.
Back in Naperville, where the Kings lived for 10 years before returning to their native California, Rich Nowell and his family were in complete shock and saddened by Tuesday's developments
"We're all numb at the present time and it's just a tragedy that somebody so kind, so sweet, so generous -- that this could happen to somebody like her, and we're all quite upset," said Nowell.
Up until just a few hours ago, the family had held onto hope that Chelsea would be found alive.
Fourteen-year-old Alex Nowell is taking the news especially hard. He said Chelsea was a mentor to him.
"She was just an amazing person. I felt like she was my sister," he said as the rest of the Nowell family sobbed in the kitchen. "She taught me a lot of things."
Chelsea was last seen Thursday, Feb. 25. before heading out to run after school. Her car was found at the Rancho Bernardo Glassman Community Park. Her cell phone, iPod and school clothes were found inside the car.
Since then, hundreds of volunteers searched the area near Lake Hodges. On Monday, law enforcement sources said an article of King's clothing was found on the southern edge of the lake.
DNA on the clothing led to the arrest of John Albert Gardner III, according to investigators. Gardner, a registered sex offender, was uncooperative with authorities and was being held without bail on suspicion of first-degree murder and rape.
He'd been previously linked to an attack on a jogger in December, according to investigators. The woman in that case got away and identified Gardner in a photo lineup.