A 120-page report both praises and criticizes the police response during the massive manhunt for Dorner.
Communication lapses were caught on tape by a patrol car dashboard camera as Dorner opened fire on two Riverside police officers.
Dorner was in a pickup truck across the intersection from officers Michael Crain and Andrew Tachias. He drove by and fired a barrage of bullets with an automatic weapon.
Dispatchers warned officers about Dorner's previous attack on LAPD officers, but it was too late: Crain was killed instantly; Tachias was critically injured and unable to move. A cab driver rushed to their aid.
The report, issued by Washington, D.C.-based Police Foundation, says communication and coordination problems between six law enforcement agencies hampered the police response as Dorner killed four people, including two civilians, Riverside officer Crain, and a San Bernardino sheriff's detective.
The Police Foundation report praises the overall work of law enforcement, but calls for immediate improvement in several areas.
Communication among all the agencies one of the biggest challenges.
"They could be solved but it's going to require a lot of funding, and I don't know that anybody is able or willing to step up to that point," said LAPD Chief Charlie Beck.
The other major challenge: the massive response when authorities cornered Dorner in a cabin in the San Bernardino Mountains. Too many officers racing to the scene created chaos and a dangerous situation.
"There were a couple of things that caused a problem for us with the self-deployment: One being the line of police vehicles on Highway 38 that ultimately blocked access to our armored vehicle and our tactical tractor," said San Bernardino County Sheriff John McMahon.
"That's a huge issue and it reinforces to us to the leaders in law enforcement that discipline is important in what we do," said Riverside Police Chief Sergio Diaz.
The LAPD, Riverside Police and San Bernardino County Sheriff's Department all say they have started implementing some of the changes listed in the report.