MARTINEZ -- A 25-year-old man is being held on suspicion of murder after striking and killing a woman Saturday on the steps of the Martinez Chamber of Commerce office, police said.

Officers arrested Jason Castillo of Concord a short time after police received a call around 7:25 p.m. reporting a man fighting with a woman in front of the chamber office on Marina Vista, said Martinez police Lt. Jon Sylvia. Police have not released the 47-year-old woman's name as they try to inform her next of kin.

Witnesses told police the assailant hit the woman and then walked away from the chamber offices, which were closed at the time of the alleged assault. Police found Castillo walking on Ferry Street in downtown Martinez.

An ambulance rushed the wounded woman to Contra Costa Regional Medical Center, where she was pronounced dead.

Police didn't release information on what may have sparked the attack. The woman's slaying remains under investigation.

Contact Joshua Melvin at 650-348-4335. Follow him at Twitter.com/melvinreport.