As the cadaver dogs begin their search, a grim reality sets in for one sheriff.

For Sheriff Robert Luna, of Los Angeles County, the first memory Altadena conjures is of the cheery crowds at the grand Christmas tree lighting ceremony he attended two years ago.

On Saturday afternoon, when the winds finally relented and the lingering fires were put out, those images were replaced by destruction and absence.

“My first thoughts are all the people that I met who love this community and think the world of it,” the sheriff said. “I’m wondering, ‘Where are they at right now?’”

It was his first time surveying the unincorporated community directly under his department’s jurisdiction. His five-car caravan, which included an entourage of deputies and the state attorney general, Rob Bonta, rolled out of the sheriff’s station, which miraculously survived the firestorm.

The first stop was the historic Farnsworth Park and its amphitheater, painted forest green and previously concealed by lush, green trees. The building adjacent to the amphitheater, which housed a community center, was reduced to its foundation. Many of the amphitheater’s seats had melted into heaps of ashy metal.

“I get depressed every time I see it,” said Capt. Jabari Williams, who is in charge of the sheriff’s station in Altadena. The venue was known for its summertime concerts.

“It’s one of the biggest events in Altadena,” Captain Williams said, stepping over debris. “I don’t know what they’re going to do now.”

Next stop was the neighborhood just west of Lake Street, another example of the blaze’s capriciousness. Only one home stood on the street, an unscathed Audi in its driveway and the property’s bushes and trees still green. Nothing but the charred carcasses of the neighbors’ homes remained on either side.

Rows of houses had vanished, and the unsettling reality that had been hinted at all week finally sank in for Sheriff Luna. The cadaver dogs were sent in on Saturday. Officials began the meticulous process of checking thousands of structures within the search area for victims.

“Unfortunately, I think we’re going to find more fatalities,” the sheriff said. “You don’t have this kind of destruction and not have that.”

He hoped people were able to escape, but the flames, stoked by hurricane-force winds, raced through the streets at tremendous speed. With the inferno in Pacific Palisades well underway on Tuesday, officials had to quickly pivot to respond to both fires.

The sheriff’s station in Altadena had just sent a search and rescue team to Pacific Palisades.

“Within 10 minutes, we got the call that there was a fire in Eaton canyon, so I immediately called them back,” said Rich De Leon, a reserve deputy sheriff who was in charge of rescue operations the day the fire broke out.

Mr. De Leon, a volunteer who lives in Altadena, came to the sheriff’s station on Saturday to lend a hand. He, like many of his fellow residents, had lost his house.