PORTLAND — A woman has been arrested in the shooting death of Eugene traffic enforcement officer whose body was found slumped against a tire of a tractor-trailer rig in rush hour traffic.

PORTLAND — A woman has been arrested in the shooting death of Eugene traffic enforcement officer whose body was found slumped against a tire of a tractor-trailer rig in rush-hour traffic.

The death Friday of Chris Kilcullen, 43, is the first of a Eugene Police Department officer in the line of duty since 1934.

Cheryl D. Kidd, 57, of Springfield, was charged with aggravated murder and remained in the Lane County Jail on Saturday without bail. A motive for the shooting was not immediately clear.

The shooting occurred at about 4:30 p.m. when Kilcullen, a 12-year veteran, tried to stop the driver of a Buick Skylark. The driver fled, and Kilcullen pursued the sedan into nearby Springfield. When cornered at a traffic light, the driver fired at least one shot from a handgun that struck Kilcullen, officials said. Police say he did not return fire.

Bobbie Clark of Springfield told KEZI-TV in Eugene that she watched the chase unfold and followed Kilcullen's motorcycle. When she arrived at the shooting site, she found Kilcullen shot. "It is so sad. They work so hard, and it's not fair," Clark said. "I was hoping she'd be the one to run into something and not him."

Springfield Police Chief Jerry Smith said his department was seeking search warrants for Kidd's Springfield apartment and her car.

"We're contacting neighbors, associates, trying to learn a little more about her," Smith said. He said his department hadn't yet found any relatives of Kidd in the area.

Kidd was cornered after the shooting on a dead-end Forest Service road near Lowell. She remained in the car for at least two hours until being coaxed from the vehicle and arrested without incident.

Late Saturday, authorities announced that a police memorial service for Kilcullen with full honors will be held Friday at 2 p.m. at Matthew Knight Arena on the University of Oregon campus.

Kilcullen was the second officer killed in the line of duty in Oregon this year. In January, Rainier Police Chief Ralph Painter was shot and killed while investigating a break-in at a stereo-installation business.

Kilcullen's father told KVAL-TV that his son was a good officer who enjoyed police work.

"He was a really good kid," John Kilcullen said. "I mean, I guess he wasn't a kid. He was real guy, and he loved his job."

Kilcullen was hired in 1998 and won employee of the month awards in May 2004 and June 2008 after conducting the most investigations, arrests, traffic citations and field interviews among Eugene police officers. He moved to the traffic unit in 2005 and was a longtime member of the department's crisis negotiation team.

Eugene Police Chief Pete Kerns on Saturday called Kilcullen's career "remarkable" and said he had earned 85 commendations in his career, even from drivers he stopped.