Authorities in San Diego followed up on a potential lead in the search for homicide suspect Christopher Dorner. NBC 7's Diana Guevara reports from Shelter Island.
An expert with the U.S. Marshals Service says it's likely that the suspect at the center of a region-wide manhunt has fled to Mexico.
Authorities have been searching up and down Southern California for Christopher Dorner, a former LAPD officer accused in the shootings of law enforcement officers and their families.
They continued the search in Big Bear Monday after the discovery of Dorner's burning pickup south of Big Bear Lake about seven hours after the shooting in Riverside.
However, Inspector Craig McClusky with the U.S. Marshals Service wrote in an affidavit that based on recent observations and in his experience, "there is probable cause to believe that Dorner has moved and traveled in interstate and foreign commerce from California to Mexico with the intent to avoid prosecution."
Among the evidence that has surfaced since the manhunt for Dorner began was surveillance of Dorner tossing several items into a dumpster behind a National City store.
On Monday, the Riverside County District Attorney's office announced that it has filed a murder charge against Dorner.
Riverside County District Attorney Paul Zellerbach announced the charge in the shooting death of Officer Michael Crain. Crain was shot Thursday while he and his 27-year-old trainee partner were sitting at a traffic light near the Riverside Freeway in a shooting that police described as an ambush.
"We felt the state of the evidence dictated there was no reason to withhold filing charges," said Zellerbach. "He's a felon at large."
Crain, who served in the U.S. Army, was 34. Funeral services for the 11-year police department veteran -- a father of two -- are scheduled for Wednesday.
"He was ambushed in such a way that he never had an opportunity to use those skills," said Riverside Police Chief Sergio Diaz. "His friends tell us how much they admired him both as a human being and a police officer."
The murder charge includes two special-circumstance allegations: the murder of a peace officer and the discharge of a firearm from a vehicle. The special circumstance allegations make Dorner eligible for the death penalty.
"Mr. Dorner has committed one of the most horrific crimes imaginable," Zellerbach said. "When those who protect us every day then become the target for violence, we as a society must become the 'eyes and ears' in assisting law enforcement in apprehending this very violent person."
Dorner was also charged three counts of attempted murder of a peace officer, according to the DA's office. The hospitalized trainee officer's identity has not been released.
"He's in a lot of pain," said Diaz. "He's going to be facing many surgeries in the coming weeks and months."
The two other attempted murder counts involve two LAPD officers allegedly attacked by Dorner in Corona about 20 minutes before the Riverside shootings. The officers were part of a security detail assigned to subjects identified in Dorner's manifesto.
Dorner also is a suspect in the Feb. 3 shooting deaths of a former LAPD captain's daughter and her fiance. He was identified Wednesday as a suspect in the shooting deaths of Monica Quan, 28, and her fiancé, Keith Lawrence, 27.
In an online manifesto that identifies several officers and their family members as part of what police call a revenge plot, Dorner repeatedly refers to Quan's father as being involved in his 2008 firing from the LAPD.
The LAPD announced a $1 million reward Sunday in the case. More than 600 tips have been received, according to the LAPD.