Officers went to 1200 Broadway Plaza after several people called 911 to report a robbery and people running out of Nordstrom at about 8:30 p.m., according to Walnut Creek police.
Witnesses told arriving officers that a male and female suspect had entered the store and grabbed armloads of purses and handbags, police said.
The store alarms were activated and the suspects pushed customers out of the way to run out of the store, police said.
One customer apparently tried to grab the male suspect's arm, police said. The suspect, later identified as Bryan Black, 42, of Oakland, sprayed the customer in the face with pepper spray.
A second customer tackled Black outside the store as he was running toward a waiting vehicle, police said.
Black allegedly tried to pepper spray the man, but the good Samaritan was able to hold him down until security guards and police arrived to take him into custody, police said.
The female drove off in a beige Ford Fusion.
Black was arrested for robbery, burglary, assault, possession of stolen property, possession of burglary tools and violating parole. One of the good Samaritans was treated for minor injuries at the scene.
The handbags were returned to Nordstrom.