Authorities in Los Angeles have offered a $1m (£630,000) reward for information leading to the arrest of a fugitive ex-policeman suspected of three murders.Christopher Dorner, 33, has been on the run for the past week, following the attacks in southern California.
A DIY shop was searched on Sunday after a reported sighting, but no trace of the suspect was found.
In an online "manifesto", Mr Dorner swore to take revenge on police officers he blamed for his 2008 firing.
Announcing the reward at a news conference on Sunday, Los Angeles Mayor Antonio Villaraigosa said: "We will not tolerate this reign of terror that has robbed us of the peace of mind that residents of southern California deserve."
'Domestic terrorism' LAPD chief Charlie Beck said it had been easy to raise the money for the reward, but added this case was different from most rewards because police believe Mr Dorner would attack again if he had the opportunity.
"This is not about catching a fugitive suspect, it's about preventing a future crime, most likely a murder," he said.
"This is an act, make no mistake about it, of domestic terrorism."
Mr Dorner, a former officer of the Los Angeles Police Department (LAPD), is suspected of killing three people, including a policeman.
Police sources revealed on Sunday they were investigating whether he had made a taunting phone call to the father of one of the victims.
Monica Quan, 28, was gunned down, along with her fiance, in her car on 3 February in Irvine, California.
Her father, Randal Quan, a retired police captain who represented Mr Dorner in a disciplinary procedure, received a phone call telling him he should have done a better job protecting his daughter, the Associated Press reported.
Police are now protecting 50 families, many belonging to former LAPD colleagues, against whom Mr Dorner has vowed revenge for ruining his career.
In his online manifesto, Mr Dorner, a former US Navy reservist, suggested that racism was rife in the LAPD.
Police are continuing a scaled-back search near Big Bear Lake, 80 miles (130km) east of Los Angeles, after the suspect's burned-out truck was found near a ski area.
Meanwhile, officials released the name of the Riverside police officer shot dead last Thursday, allegedly by Mr Dorner.
The funeral of Michael Crain, a 34-year-old ex-Marine who had served in the department for 11 years, is due to be held on Wednesday.
Crain was in a squad car on routine patrol when the suspect allegedly opened fire, seriously wounding another police officer, who is expected to survive.
In a separate shooting last Thursday, Mr Dorner is accused of opening fire on two other police officers, grazing one of them.
At the weekend, Chief Beck said the department would re-examine the case that led to Mr Dorner losing his job, a key grievance in the suspect's online essay.
He was fired for making false statements, after making a complaint against his field training officer, saying she had kicked a suspect during an arrest.
Chief Beck said re-opening the investigation was not a response to Mr Dorner's demands.
"I do this not to appease a murderer," Mr Beck said in a statement.
"I do it to reassure the public that their police department is transparent and fair in all the things we do."