By Shirin Rajaee

SIERRA (CBS13) – Another tragic accident at a Sierra ski resort, this time involving a mother and her seven-year-old son. The two were killed when a massive chunk of snow fell from a roof and buried them underneath it.

“Very horrible. I mean, a young kid and mom. Oh God,” said Ron Lundy, a neighbor in the family’s Bay Area neighborhood.

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The accident happened Sunday at Kirkwood Ski Resort, making this the 3rd and 4th death since a major snowstorm hit the region last week.

“They were two very wonderful members of our community. Olga was a very involved parent and we’re just so saddened by the loss,” said Keelee Wrenn with the French American International School.

The Alpine County Sheriff’s Department is calling it a “freak accident.”

Fifty-year-old Olga Perkovic and her seven-year-old had just returned to their Kirkwood condo after a day of skiing when the snow, the size of a trailer slid off the roof. The impact crushed them both.

Hours later, a neighbor spotted ski gloves in the snow, and called 911. Perkovic and the boy were airlifted to the hospital and declared dead.

At their home, flowers were being delivered Tuesday and a poster board was filled with messages.

Meanwhile, the two deaths add to an already tragic week in the Sierra.

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“This is a great example of what can be a very dangerous situation on a house,” said Sgt. Ted Bier with Truckee police.

Truckee police are warning folks that when temperatures warm up, snow can melt off rooftops.

“The snow can let go at any time if there’s someone underneath it, that’s a few hundred pounds falling on somebody, it can cause death or injury,” said Bier.

“As soon as we get that heat and it hits those roofs that snow is gonna slide off … it’s got all that extra weight up there,” said former ski patrol, Patrick Paul Zarubian.

According to Kirkwood Ski Resort, the last storm dumped 6 feet in the snow in the area, also raising concerns about the proper cars of propane tanks.

“At least take a look that the lines coming from the propane tank to the house and make sure they’re uncovered,” said Sgt Bier.

Authorities also add that the mother and son appeared to have skied an alternate route home Sunday that took them between buildings.

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“You gotta really pay attention when you’re going in the back country. Even though it’s beautiful weather and the sun’s out, you just have to be cautious,” said Zarubian.