Faced with regular barrages of gunfire, officers confronting suspected killer Christopher Dorner lobbed incendiary tear gas into the cabin where Dorner allegedly was holed up, said law enforcement officials with knowledge of the situation.

The cabin caught on fire and authorities believe Dorner was burned inside. A body was discovered but authorities have not confirmed it was Dorner.

Law enforcement sources said the officers got into several gun battles with Dorner during a nearly four-hour siege at the cabin in the Big Bear area. The standoff began when Dorner allegedly fatally shot a San Bernardino County sheriff’s deputy and seriously injured another.

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SWAT officers surrounding the cabin were under a "constant barrage of gunfire," one source said. “He put himself in that position. There weren’t a lot of options.”

Hoping to end the standoff, law enforcement authorities first lobbed "traditional" tear gas into the cabin. When that did not work, they opted to use CS gas canisters, which are known in law enforcement parlance as incendiary tear gas. These canisters have significantly more chance of starting a fire. This gas can cause humans to have burning eyes and start to feel as if they are being starved for oxygen. It is often used to drive barricaded individuals out.

If the body is identified as Dorner’s, the standoff would end a weeklong manhunt for the ex-LAPD officer and Navy Reserve lieutenant suspected in a string of shootings following his firing by the Los Angeles Police Department several years ago. Four people have died in the case, allegedly at Dorner’s hands.

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Beck said he would not consider the manhunt over until the body was identified as Dorner. Police remained on tactical alert and were conducting themselves as if nothing had changed in the case, officials said.

The injured deputy is expected to survive but it is anticipated he will need several surgeries. The names of the two deputies have not been released.

Just before 5 p.m., authorities smashed the cabin's windows, pumped in tear gas and called for the suspect to surrender, officials said. They got no response. Then, using a demolition vehicle, they tore down the cabin's walls one by one. When they reached the last wall, they heard a gunshot. Then the cabin burst into flames, officials said.

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Last week, authorities said they had tracked Dorner to a wooded area near Big Bear Lake. They found his torched gray Nissan Titan with several weapons inside, they said, and the only trace of Dorner was a short trail of footprints in newly fallen snow.