The man, whose name has not been released, is suspected of gunning down a 47-year-old woman in Walnut Creek at about 1:30 p.m. in the 1900 block of First Avenue, police said.
The woman, whose name also was not released, had "a dating relationship" with the suspect, according to police.
After allegedly shooting her multiple times, the suspect fled in a Chevrolet sedan, abandoning the car about a half-mile away on Lynvale Lane, police said.
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The man is still in his car, which is surrounded by officers near the corner of Howe and Old Orchard roads, according to police.
Residents cannot go in and out between Howe Road and Center right off Highway 4.
John Muir Elementary School is closed and there are some county offices that are closed because of the standoff.
A Chevron has also been closed since Thursday night.
The standoff began Thursday at about 8 p.m. after Walnut Creek officers spotted his car and pulled him over, according to Walnut Creek police spokesman Lt. Tom Cashion.
The man was the subject of an intensive manhunt after he allegedly shot a woman to death at about 1:30 p.m. in the 1900 block of First Avenue near the Lindsay Wildlife Experience.
Officers from multiple agencies used dogs and a California Highway Patrol helicopter to search for the man, who is believed to have abandoned the car he was using, fled to a home on San Luis Road in Walnut Creek, got into another car and drove to Martinez, where officers were able to pull him over, according to Cashion.
The SWAT team used a robot to send the suspect water and also sent him cell phones so they could talk to him.
The mother of a resident says she tried to check in on her daughter but had no luck.
"Because this has been going on since last night, she says 'You're not going to believe this but I'm still stuck inside,'" one relative of a resident told ABC7 News.
Police have not yet revealed a possible motive for the killing, but Cashion said investigators believe the suspect knew the victim.
A nice citizen brought the officers on this Martinez standoff donuts! And they shared with the media! 😋 pic.twitter.com/0jMKFhoB0I— Amy Hollyfield (@amyhollyfield) April 28, 2017
The Bay City News contributed to this report.