(CNN) Eight Los Angeles police officers who collectively fired 107 shots at two women delivering newspapers in a truck that police had mistaken for one belonging to renegade ex-cop Christopher Dorner will not face criminal charges, the Los Angeles County District Attorney's Office said Wednesday.

Among the key findings submitted by the office's justice system integrity division: Officers were on a heightened state of alert, given Dorner's previous violence against police and a report that Dorner was in the area; the officers were conducting a security detail "with limited planning or tactical instruction"; the truck that Margie Carranza and her then-71-year-old mother, Emma Hernandez, were driving was similar to Dorner's; and the sound of the women's newspapers slapping against driveways resembled gunshots.

At the time of the February 7, 2013, shooting, Dorner had issued a manifesto declaring war on police after exhausting his appeals to be reinstated following his ouster from the Los Angeles Police Department.

He claimed racism was behind his firing and killed four people and wounded three others on his vendetta rampage.

According to the district attorney's 52-page memorandum, which included 29 largely redacted pages and four pages with minor redactions, Dorner was "hunting his former colleagues" and seemed to accept he would die.

The officers have claimed self-defense and said they used what would've been justifiable force to detain a fleeing felon. LAPD Chief Charlie Beck has said he didn't believe the officers' use of force was up to his standards.

Women received settlements

"I sympathize with the officers, but I have a very high standard for the application of deadly force, and the shooting did not meet that standard," Beck told reporters a year after the shooting.

All eight violated department policy, and "discipline could be anywhere from extensive retraining up to termination," the chief said, adding that the officers were taken off field duty. State law prohibited him from providing specifics about the punishment, he said.

Despite the chief's finding -- and despite the City Council awarding the women a $4.2 million settlement and, separately, $40,000 to replace their bullet-riddled pickup in the months following the shooting -- the county district attorney's office noted that the chief's decision required a lower burden of proof than did the leveling of criminal charges.

"Any administrative discipline imposed on those officers is extraneous to the findings in this memo," it says.

The officers were dispatched to the unfamiliar territory of Torrance, south of Los Angeles, to provide a security detail for LAPD Capt. Justin Eisenberg, who was a member of the board of rights that voted to fire Dorner, prompting Dorner to mention him specifically in his manifesto, the memo says.

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There, the officers were "ordered to conduct a protective details with limited planning or tactical instruction and limited resources."

They had received a description of Dorner's truck: a light-gray Nissan Titan with the license plate 8D83987.

It was about 5:10 a.m. when Carranza and Hernandez entered the neighborhood in a blue four-door Toyota Tacoma with a license plate that began "8D," followed by a different sequence of numbers, the memo says.

The windows, save the windshield, were tinted. Carranza was driving, at what she estimated was 5 mph, and Hernandez was sitting in the back seat, handing newspapers to Carranza so she could toss them into driveways.

107 shots

Carranza would later recall for investigators that she saw a police car with its doors open in one of the neighborhood's driveways, but no officers.

"She heard a large number of gunshots coming from behind her. Carranza stopped her car due to the shots being first. Gunshots began to strike her truck. She screamed out and tried to yell that she was working. She felt the tires of the car 'explode' and glass passed by her face. Carranza was in a panic. Hernandez told her, 'Don't be afraid,' " according to the memo.

When they exited the vehicle on the officers' orders, Carranza realized her mother had been shot in the lower back and scapula. Carranza had suffered cuts to her hand, "likely from broken glass," the memo says.

According to the memo: "There was a palpable degree of tension and fearful apprehension amongst the law enforcement personnel gathered to conduct this investigation."

Newspapers sounded like gunshots?

Beck, who has called the incident a "tragic cascade of circumstance that led to an inaccurate conclusion by the officers," has said that one of the officers mistook the sounds of the newspapers hitting driveways for gunshots.

The investigative memo reiterates that claim and says that once the officers began firing, the sound "likely reverberated," giving the officers the impression that someone in the truck was firing back.

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A Hermosa Beach police officer who responded to the scene with his partner and was not involved in the shooting explained the phenomenon as follows, according to the memo:

When an officer "hears the flick of a paper slapping against the wet, foggy ground, and what do you hear? You hear that pop. I mean, to me, that's all it takes. Shots fired, taking rounds. ... There's a pop to (a newspaper) when it hits it right and if that car is swerving side to side and goes by the house and that paper goes flying out this window, it can easily sound like a shot and some poor guy who has been up for 20-something hours, you know?" the officer is quoted as saying.

The memo points out that courts "have warned against second-guessing the split-second judgment of a trained police officer merely because that judgment turns out to be mistaken."

It also cites the California appellate case, People v. Lucero, which found, "An honest and reasonable belief in the existence of circumstances, which, if true, would make the act for which a person is charged an innocent act, has always been held to be a good defense."