By Gillian Flaccus

Associated Press

LOS ANGELES — Communication and coordination problems between at least a half dozen regional law enforcement agencies impeded efforts to stop cop-turned-killer Christopher Dorner and possibly endangered lives during his 10-day revenge mission across Southern California last year, according to an independent report released Monday.

The report, (can be seen in full here) released by the District of Columbia-based Police Foundation, praised the overall work of police and sheriff's officials in an area encompassing four counties but identified several areas for improvement. It especially called for all regional agencies to immediately upgrade their communication systems so officers in different agencies across regions can talk to one another.

In one chilling example, police officers in Riverside were unaware that Dorner had just opened fire on two LAPD officers in the neighboring city of Corona just minutes before they themselves were ambushed at a red light. The information was not relayed for 10 minutes and the LAPD officers were relying on cellphones to communicate because they were too far out-of-range for their police system to work.

One of the Riverside officers died and the other was injured. The two LAPD officers survived.

The online report includes a snippet of previously unreleased video from the Riverside officers' patrol car that shows Dorner's truck approaching through the intersection, followed by a bright flash of gunfire as he opened fire. The patrol car then slowly rolls through the intersection.

"The Riverside Police Department was under attack before officers even knew Dorner was there. As the dispatcher began broadcasting the urgent alert from the Corona incident, she was interrupted by a frantic call of 'officer down,'" according to the report.

The study's authors also found that too many officers raced to the scene when authorities had Dorner holed up in a cabin in the San Bernardino Mountains, creating a dangerous situation and making narrow mountain roads nearly impassable for the SWAT teams in charge.

"Witnesses said hundreds of law enforcement officers responded to the scene, some from over 100 miles away. Valuable time was wasted managing the vast number of ill-prepared police officers who left the much warmer coastal and inland climates of Southern California for the extreme cold of a mountain ski resort at 7,000-foot altitude," the authors said. "As one chief of police would later declare, 'I had no business going up there.'"

A turf war between police in Irvine and Riverside County sheriff's officials over who would do forensics analysis on Dorner's abandoned and burnt-out truck also delayed the investigation into the killings of Dorner's first two victims, a retired LAPD captain's daughter and her fiance.

The two were found shot dead in a car in the parking lot of an Irvine condominium complex and the killings were eventually linked to Dorner, who had posted a manifesto online outlining his intent to target and murder police officers.

Police agencies across Southern California spent 10 frantic days tracking Dorner as he moved from suburban Orange County, to San Diego and back north to the remote and snow-covered mountains east of Los Angeles.

Dorner, who had been fired from the Los Angeles Police Department, eventually shot himself in the burning cabin where he holed up.

He killed four people during his revenge mission, including the couple in Irvine, the Riverside police officer who was ambushed while on patrol, and a San Bernardino County sheriff's detective who was shot during the final gun battle.

The LAPD thanked the report's authors and said they had also been conducting an internal review into the event, which was "unprecedented in modern law enforcement history."

"As we review this report, and continue to reevaluate our law enforcement response, let us not forget the lives that were lost and the families that were torn apart by this killer," LAPD Police Chief Charlie Beck said.

Copyright 2014 The Associated Press