Posters across the community and on a Facebook page with over 51,000 fans describe the 17-year-old King as 5-foot-5 and 115 pounds with strawberry blond hair and blue eyes.
"Because it was so out of character for Chelsea not to tell us or call us and say I'm going to be late ... we just had that feeling," her father Brent King told reporters Monday.
His wife Kelly King called 911 as Brent drove to the park, where he found Chelsea’s belongings, including her cell phone, inside her BMW, then spotted a running trail into the woods.
Calling Out for His Daughter"I took off and ran down the trail as far as I could run, calling out for my daughter at the top of my voice in every direction," recalled Brent King, who had last seen his daughter the previous evening, after she played french horn in a school concert.
On Saturday afternoon, more than 1,000 searchers combed San Diego's Rancho Bernardo Community Park in a heavy rainstorm, says Susan Plese, a spokeswoman for the San Diego County Sheriff.
"We're still looking for her in the same area we have been," Plese tells PEOPLE. "The response has been just tremendous."
On Sunday, investigators found evidence that they say links King's disappearance to convicted sex offender John Albert Gardner III, 30, and arrested him near Escondido, Calif., on suspicion of rape and murder. Officials would not discuss the evidence. Gardner has not yet been charged, although his arraignment is scheduled for Wednesday.
Another Victim?San Diego County Sheriff Bill Gore also tells reporters there's "a strong possibility" Gardner attacked a female jogger in the same park on the morning of Dec. 27. He says his investigators are trying to determine if Gardner abducted Amber Dubois, 15, who disappeared Feb. 13, 2009, while walking to Escondido High School and has still not been found.
At Poway High School on Monday, angry and fearful students attended counseling, wore blue shirts to represent the color of Chelsea's eyes, and tied blue ribbons around light poles. "We're still hoping for the best, but we're fearing the worst," counselor Traci Barker-Ball tells the Union Tribune.