Thousands of heavily armed officers patrolled highways throughout Southern California, while some stood guard outside the homes of people police say Dorner vowed to attack. Electronic billboards, which usually alert motorists about the commute, urged them to call 911 if they saw him.
Police Chief Charlie Beck urged Dorner to surrender at a news conference held amid heightened security in an underground room at police headquarters.
"Of course he knows what he's doing; we trained him. He was also a member of the Armed Forces," he said. "It is extremely worrisome and scary."
While in the Naval Reserves, Dorner earned a rifle marksman ribbon and pistol expert medal. He was assigned to a naval undersea warfare unit and various aviation training units, according to military records, taking a leave from the LAPD to be deployed to Bahrain in 2006 and 2007.
He wrote that he would "utilize every bit of small arms training, demolition, ordinance and survival training I've been given," the manifesto read.
The nearly 10,000-member LAPD, a force Dorner was part of from 2005 to 2008, dispatched officers to protect more than 40 potential targets, including police officers and their families. The department also pulled officers from motorcycle duty, fearing they would make for easy targets.
The hunt also led to two errant shootings in the pre-dawn darkness Thursday.
LAPD officers guarding a target named in the manifesto shot and wounded two women in suburban Torrance who were in a pickup truck, authorities said. Beck said one woman was in stable condition with two gunshot wounds and the other was being released after treatment.
"Tragically we believe this was a case of mistaken identity by the officers," Beck said.
Minutes later, Torrance officers responding to a report of gunshots encountered a dark pickup matching the description of Dorner's, police said. A collision occurred and the officers fired on the pickup. The unidentified driver was not hit and it turned out not to be the suspect vehicle, they said.
In San Diego, where police say Dorner tied up an elderly man and unsuccessfully tried to steal his boat Wednesday night, Naval Base Point Loma was locked down Thursday after a Navy worker reported seeing someone who resembled Dorner.
Navy Cmdr. Brad Fagan said officials believe Dorner had checked into a base hotel on Tuesday and left the next day without checking out. Numerous agencies guarded the base on Thursday. Fagan said Dorner was honorably discharged and that his last day in the Navy was last Friday.
Nevada authorities also joined the search, because Dorner owns a house nine miles from the Las Vegas Strip, according to authorities and property records.
In Big Bear, Dorner's pickup was taken to be processed at a crime lab Thursday evening and examined by investigators from multiple agencies.
Jackie Holohan, who runs a vacation rental company in Big Bear Lake, said visitors weren't dissuaded from coming to the mountain resort despite the intensive manhunt.
"The only ones who have called want to make sure if they can get up the mountain," Holohan said.
The manhunt was affecting some local businesses. A couple of fast food restaurants shut their doors and only took drive-in customers, and the main shopping avenue had light foot traffic.
Sheriff's officials said deputies and officers had combed some 200 homes in the area and intended to search some 200 more, with extreme wariness knowing they were likely to be treated as targets as well as hunters.
Dorner's writings suggested he did not expect to live through the ordeal.
"Unfortunately, I will not be alive to see my name cleared," he wrote at one point in his manifesto, later saying, "Self-preservation is no longer important to me. I do not fear death as I died long ago."
Associated Press writers contributing to this report include Jeff Wilson, Bob Jablon, Greg Risling, Shaya Tayefe Mohajer, Linda Deutsch and John Antczak in Los Angeles, Ken Ritter in Las Vegas, and Elliot Spagat and Julie Watson in San Diego.