An alarm system notified firefighters of the blaze at the two-story home on Deer Meadow Drive at about 11:15 a.m.
Normally when an alarm system is activated, an alarm sounds inside the home to give residents time to escape, Price said.
"The problem was the fire burned above them in the attic where there's no detectors, and then collapsed into the second floor," he said.
When firefighters arrived, they found Benjamin Litman, 19, deceased inside the home.
Litman's father, Robert Litman, was also found unconscious in a bedroom. He was treated at the scene before being transported to Santa Clara Valley Medical Center where he was in critical condition this morning, hospital spokeswoman Joy Alexiou said.
The fire was extinguished about an hour after it started, Price said.
It caused an estimated $2 million in damage - $1.5 million to the structure of the home and $500,000 to its contents, he said.
Investigators have not yet been able to determine the cause.
An autopsy was being conducted this morning on Benjamin Litman, and investigators are hoping to determine how he died by this afternoon, according to the Contra Costa County coroner's office.