Updated

In what officials are calling a freak accident, a mother and her 7-year-old son were fatally buried in Northern California on Sunday by a falling chunk of snow the size of a trailer.

The massive block of snow fell from a roof and blanketed the two just steps from the front door of their mountain condo, authorities said.

Olga Perkovic and her son Aaron Goodstein had been skiing in the Sierra Nevada near the Nevada state line, the Alpine County Sheriff's Department said.

They were returning home when the snow chunk fell, burying them under about 3 feet of snow.

"It was a freak accident," Undersheriff Spencer Pace said Monday.

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He said warming temperatures often cause snow to slide off roofs, occasionally injuring people.

But he said neither he nor the sheriff can recall sliding snow ever killing anyone in the three decades they've been there.

Pace said Perkovic's mother, who was staying in the condo with the family of five, reported the pair missing at about 6:40 p.m. Sunday.

Rescuers searched the nearby Kirkwood Ski Resort for hours because the pair's last know location was a ski lift where they had scanned their tickets at about 4 p.m.

Pace said it appears the two skied an "alternate" route home from the slopes that took them between buildings on a path that is unpaved in the summer.

At about 9 p.m., a neighbor spotted ski gloves next to the condo, realized they were beneath the snow and called 911.

The mother, 50, and son from San Francisco were airlifted to a hospital, where they were declared dead, Pace said.

They were the third and fourth to die at California resorts since a major snowstorm late last week.

The Associated Press contributed to this report.