Officers decided to end the standoff at the cabin where Christopher Jordan Dorner was believed to be holed up because they considered him a severe and immediate threat to officers and the public, law enforcement authorities said Tuesday night.

In typical barricade situations with armed suspects, commanders at the scene try to calibrate their response between negotiating a peaceful resolution over an extended period and taking quick action.

But given that Dorner, 33, had allegedly killed three people, including a Riverside police officer, and then mortally wounded a San Bernardino County sheriff's deputy in a fierce gun battle with law enforcement Tuesday afternoon outside the cabin, authorities felt they had to move.

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"We had to end this quickly," a law enforcement source told The Times.

As authorities moved into the cabin late Tuesday afternoon, they heard a single gunshot.

According to a law enforcement source, police had broken windows, fired tear gas into the cabin, and urged Dorner, over a loud speaker, to surrender. When they got no response, officers deployed a vehicle to rip down the walls of the cabin "one by one, like peeling an onion," a law enforcement official said.

By the time officers got to the last wall, authorities heard a single gunshot, the source said. Then flames began to spread through the structure, and gunshots, probably set off by the fire, were heard.

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A tall plume of smoke rose as flames consumed the wood-paneled cabin. Hundreds of law enforcement personnel had swooped down on the site near Big Bear after the gun battles between Dorner and officers broke out in the snow-covered mountains, where the fugitive eluded a massive manhunt since his truck was found burning in the area late last week.