His presence was detected Tuesday when two women arrived at the cabin to clean it and were tied up. Dorner stole their car and fled. One of the women eventually worked herself free and alerted police, according to California Fish and Game Department spokesman Andrew Hughan. The Fish and Game officers were assisting in the dragnet for Dorner.
Dorner crashed that car and hijacked a pickup truck as officials from the state Fish and Game Department pursued him.
"I saw some movement in the trees and it was Christopher Dorner," Rick Heltebrake, the pickup's driver, told ABC News. "And he came out onto the road, out of the snow. And he was dressed in all camouflage and had a big assault, sniper-type rifle. And he had a vest on, like a ballistics vest.
"He was dressed up to do some damage it looked like," Heltebrake said. "He said, 'I don't want to hurt you. Just get out and start walking up the road and take your dog with you.'"
Dorner then took off into the woods on foot, where sheriff's deputies pursued him to a rental cabin in which he barricaded himself and began firing.
"There were rounds being fired," McMahon told reporters Wednesday evening. "It was absolutely incredible. It was like being in a war zone."
McMahon called the deputies at the scene "heroes" for persisting in the face of fire from the cabin, noting, "The rounds kept coming but the deputies did not give up."
Some local television stations broadcast police scanner traffic of the firefight, punctuated by the sound of automatic gunfire.
"It was horrifying to listen to that firefight and to hear those words," said LAPD spokesman Lt. Andrew Neiman. "'Officer down' is the most gut-wrenching experience that you can have as a police officer."
Over the course of the next five hours, heavily armed SWAT teams with tank-like vehicles surrounded the cabin, even firing tear gas inside, but never entered the building.
Cops said they heard a single gunshot go off from inside the cabin just as they began to see smoke and fire. Later they heard the sound of more gunshots, the sound of ammunition being ignited by the heat of the blaze, law enforcement officials said.
Dorner is accused of killing four people, including the deputy shot on Tuesday. Last Thursday, he allegedly gunned down Riverside police officer Michael Crain, who was laid to rest today.
Crain's shooting and the discovery of an online manifesto pledging to kill dozens of cops launched the dragnet.
Dorner is also suspected of killing Monica Quan and her fiance, who were found shot to death Feb. 3. Quan was the daughter of former LAPD Capt. Randal Quan, who was mentioned as a target of Dorner's fury in the manifesto.
In the 6,000-word "manifesto," Dorner outlined his anger at the Los Angeles Police Department for firing him, and made threats against individuals he believed were responsible for ending his career with the police force five years ago. Dorner's grievance with police goes back five years, to when he was fired after filing what the LAPD determined to be a false report accusing other cops of brutality.
The LAPD assigned 50 protection details to guard officers and their families who were deemed possible targets. The LAPD said today it would maintain the details until Dorner's body was positively identified.
ABC News' Lawrence Dechant contributed to this report.