Dorner was heavily armed and seeking revenge for losing his job. He murdered four people before taking his own life during a fiery standoff in the San Bernardino Mountains.
One San Bernardino County sheriff's deputy was shot during the chaos and survived.
He remembers every moment of that day.
"Everyone was on high alert at that point and you have to be," said Alex Collins.
At first, Collins was not involved in the search because he was on paternity leave, caring for his newborn.
When Dorner's truck was spotted near Big Bear, which was where Collins was stationed at the time, he knew he had to go in.
"You have someone out there murdering innocent people, murdering cops ... if it's not us, who's it going to be?" he said.
Six days into the massive search, Dorner was finally discovered. He was spotted speeding down Highway 38 in a stolen vehicle.
As he turned onto Glass Road and down into Seven Oaks, law enforcement lost track of him, but they knew he was close by.
"We knew what the outcome was, whoever found him, what it was going to be, that he was going to try and kill anybody who stopped him," recalled Collins.
Little did he know it would happen to him.
"The first round actually hit me in the face," he recalled. "Next to my left nostril, went through the roof of my mouth, blew my teeth out, through my tongue. My chest was just like ... it felt like it was burning, and then all this blood is like building up in my mouth."
As Collins sat in pain, horrible thoughts were running through his head.
"It's not supposed to go down like this," he said. "Like, it's not ... especially up there for all those days, you know? Running all these scenarios through your mind and through your head, like me dying on the side of a mountain row like freezing ... it was not one of the scenarios that I envisioned. I left my wife with this two-week-old baby. I was like, 'What do I do?'"
Det. Jeremiah Mackay was killed that day and Collins was shot four times, but he recovered.
He's now a sergeant with the San Bernardino County Sheriff's Department and credits his partners that day with saving his life, pulling him to safety despite the gunfire.
"Those guys are heroes," he said. "I wouldn't be here if it wasn't for them. Everyone involved, you know, saved my life and they tried to save Jeremiah, too. So totally selfless act and my kids have a dad because of them."
ABC7 retraced Dorner's deadly trail in a special documentary, "True Crime: The Manhunt for Christopher Dorner." You can stream it now on ABC7 or wherever you stream.
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