This post has been corrected by the LA Times as noted below.
A California Highway Patrol officer is in grave condition and an motorist has died after a freeway shootout in Contra Costa County on Tuesday morning, law enforcement sources said.
The exchange of gunfire took place about 8:30 a.m., moments after the officer pulled over a motorist in a green Jeep Wrangler on Interstate 680 just south of Walnut Creek, said Contra Costa County sheriff's spokesman Jimmy Lee.
The identity of the officer, who is assigned to the Contra Costa field office, was not immediately released. He was taken in grave condition to John Muir Medical Center.
The driver almost immediately pulled out a gun and began shooting at the officer, Lee said. A second officer who arrived at the scene shot the motorist, who was later pronounced dead at the same hospital.
"We are still trying to determine the exact reason for the traffic stop," Lee said.
The CHP closed a section of southbound Interstate 680 for hours as authorities conducted an investigation. Joining the CHP were the Contra Costa County Sheriff's Department and the district attorney's office. Northbound lanes were also closed but were open by early afternoon.
[For the Record, 8:04 p.m., Sept. 4: A previous version of this post said that the CHP officer died. Sources say that he is brain dead, but is being kept on life support.]
UPDATED STORY: 1:52 EDT, Sept. 5, 2012
The California Highway Patrol identified the officer who was shot alongside I-680 during a routine traffic stop Tuesday morning as Kenyon Marc Youngstrom (pictured below).
Youngstrom is reportedly on life support at John Muir Medical Center in Walnut Creek surrounded by family and fellow officers.
The man he pulled over was also shot in the incident. That still unidentified man later died at the hospital.
Investigators have scheduled a 11 a.m. news conference Wednesday to update the case. It is expected they will release more information about the suspect, including his name.
For now, here is what we know about the incident: Contra Costa County Sheriff's spokesman Jimmy Lee said two CHP officers in two separate patrol cars pulled over a driver of a green Jeep Wrangler at 8:19 a.m.
During the stop, Lee said the Jeep driver pulled out a gun and opened fire on Youngstrom. The second officer then returned fire on the driver, who later died.
Lee said there was a dash camera inside one of the patrol cars and the video was being analyzed.
Youngstrom, a 7-year veteran of the CHP and a former member of the U.S. Army Reserve, is based out of the Martinez office of the highway patrol. He has a wife and four children.
On Wednesday, three men stood at the entrance of the CHP office holding American flags. They said they wanted to show officers arriving to work today that they had their support.