Dorner, 33, a former LAPD officer, has evaded authorities since Wednesday night when he was named as the suspect in the slaying of an Irvine couple, a crime that preceded a wave of violence.

Meanwhile, an associate of Dorner was being tracked by investigators, according to court records that suggest Dorner may have received help as he eluded a massive law enforcement dragnet.

Officers have crisscrossed California pursuing tips about Dorner's possible whereabouts and serving warrants at homes in Las Vegas and Point Loma.

Law enforcement sources told The Times that officials have confirmed the man in the video is Dorner. He spent $5 to $10 to fill up a scuba tank, the sources said. Investigators have also reviewed store receipts.

Neiman said detectives were examining video that might show Dorner purchasing scuba gear at a Sport Chalet store in Torrance days before his alleged killing spree began.

U.S. Marshal's officials said in court papers that Dorner could have fled to Mexico. In Tijuana, Dorner was listed as one of the most wanted fugitives. But LAPD Lt. Andy Neiman said that was only one of many locations authorities were considering.

A second source said there was an active crime scene but did not have details.

It was not immediately clear whether Dorner was in custody.

The shooting occurred after Dorner burglarized a home, tied up a couple and stole their car, the source said.

Christopher Dorner was engaged in a shootout with federal authorities in the Big Bear area Tuesday, a law enforcement source told The Times.

A criminal complaint filed in federal court raises the possibility that Dorner may have been assisted by an associate identified as "J.Y."

DOCUMENT: Read the manifesto

Statewide alerts have been issued in California and Nevada, and border authorities have been alerted. The Transportation Security Administration also issued an alert urging pilots and other aircraft operators to keep an eye out for Dorner.

The search turned to Big Bear last week after Dorner's burning truck was found on a local forest road.

At the search's height, more than 200 officers scoured the mountain, conducting cabin-by-cabin checks. It has since been scaled back: About 30 officers were involved Monday and the San Bernardino County Sheriff's Department said about the same number would be out again Tuesday.

INTERACTIVE MAP: Searching for suspected shooter

"The search for Christopher Dorner will continue until he has been apprehended or it has been determined that he is no longer on the mountain," San Bernardino County Sheriff John McMahon said Tuesday.

Authorities also asked residents in the Big Bear area with security cameras at their homes to review any video recorded after midnight Feb. 7 to see if images of Dorner had been captured.

A criminal complaint filed in federal court raised the possibility that Dorner may have been assisted by "a known associate" -- identified only as "J.Y." -- with a family member who owns a property in the San Bernardino Mountains. The exact relationship between Dorner and J.Y. was not detailed in the document.

DOCUMENT: Feds say Dorner may have fled to Mexico

The court records also provide new details as to why federal authorities developed "probable cause" that Dorner may have been trying to flee to Mexico as the law enforcement authorities were widening their dragnet.

Dorner allegedly attempted to steal a boat in San Diego and, after subduing the captain, said he was taking the vessel to Mexico, according to an affidavit filed with the criminal complaint in federal court in Los Angeles. Dorner is accused of telling the captain that he could recover his boat in Mexico.

"The attempt failed when the bow line of the boat became caught in the boat's propeller, and the suspect fled," according to the affidavit by U.S. Marshals Service Inspector Craig McClusky.

After authorities interviewed the boat captain early Thursday, they found Dorner's wallet and identification cards "at the San Ysidro Point of Entry" near the U.S.-Mexico border, according to the court records. That same day, a guard at the Point Loma Naval Base told authorities he had spotted a man matching Dorner's description trying sneak onto the base, the records said.

Federal authorities told The Times on Monday night that the court papers reflected their thinking at the time, but they stressed that Dorner could be anywhere.

A Tijuana hotel was searched Monday after Mexican authorities received vague information Dorner might be in the area, sources familiar with the investigation said. Dorner was not found, they said.

Dorner allegedly threatened "unconventional and asymmetrical warfare" against police in a lengthy manifesto that authorities say he posted on Facebook. The posting named dozens of potential targets, including police officers, that Dorner allegedly threatened to attack, according to authorities.

The records state that the manifesto was discovered by authorities Wednesday, three days after the slaying of the two Irvine victims: Monica Quan, a Cal State Fullerton assistant basketball coach, and her fiance, Keith Lawrence, a USC public safety officer.

Quan was the daughter of a retired LAPD captain whom Dorner allegedly blamed in part for his firing from the force in 2009.

The federal documents also provide new details on Dorner's alleged attack against officers early Thursday in Riverside County.

The first shooting was in Corona after an eyewitness reported a person matching Dorner's description at a gas station, telling an LAPD officer "who was detailed to the area to protect one of the officials whom Dorner had threatened," according to the court records.

"When the officer drove by the gas station, the suspect exited his vehicle and fired an assault rifle at the officer, hitting the officer's vehicle," according to the court records.

The LAPD later said the officer received a grazing wound.

About 30 minutes later, Dorner opened fire on Riverside police officers "who were in the area searching for Dorner," the documents said. On that detail, the account conflicts with a statement provided to the media by Riverside police officials, who said the officers were stopped at a red light and were not looking for Dorner.

Riverside Officer Michael Crain, 34, a married father of two who served two tours in Kuwait as a rifleman in the Marines, was killed in the attack. His partner remains hospitalized, Police Chief Sergio Diaz said, and it was unclear if he would be able to return to active duty.

Dorner was charged Monday with one count of murder, with special-circumstance allegations in the killing of a peace officer and the discharge of a firearm from a vehicle, in connection with Crain's death. He faces three additional charges of attempted murder.

Riverside Dist. Atty. Paul Zellerbach said because of the special-circumstance allegations, Dorner could be eligible for the death penalty if convicted.

ALSO:

Dorner surrounded by police in cabin after gun battle



Dorner gun battle: 2 officers shot, 'deputies are everywhere'

2 officers hurt in Big Bear shootout with Dorner, officials say

-- Andrew Blankstein