Investigators yesterday fielded tips, interviewed potential witnesses and scoured through video tapes for evidence that would lead them to the assailant or assailants. They have not yet identified a suspect or the suspect's vehicle, nor have they determined what kind of weapon was used.

Killed was field-training officer Timothy Brenton, 39, an eight-year veteran. Rookie officer Britt Sweeney, 33, suffered a minor injury. The two were discussing a routine traffic stop while parked in downtown Seattle when their police cruiser was struck several times by gunfire shortly after 10 p.m., officials said.

Assistant Police Chief Jim Pugel said Brenton died instantly. Sweeney ducked, and a bullet grazed her back. She then called for help and returned fire, Pugel said.

"This is an assassination, and every resource is being used to bring it to a conclusion," Pugel said.

Brenton became the city's first officer killed in the line of duty since 2006, and Saturday's shooting was the first intentional homicide of an officer since 1994, police officials said.

Pugel said there had been no threats against Brenton and no indication the assailants were looking for him.

Sweeney was taken to the hospital but was later released and is at home. She joined the force about six months ago, and had graduated from the academy just weeks ago.

Brenton had been with the department for eight years. He is survived by his wife and two children, ages 11 and 8, officials said. His father and uncle are retired Seattle police officers.

"Everybody loved him," the officer's uncle, Jon Brenton of Kingston, Wash., told the Seattle Times. "I don't think there was any reason anybody would come after him."

Seattle Mayor Greg Nickels described the shooting as "cold-blooded."

"Our community is in shock at this brutal and senseless crime," Nickels said. "The killing of someone who protects our public safety is universally condemned, and our city is united in rejecting this violence and supporting the men and women in uniform."