The getaway car, a sport utility vehicle, was found abandoned a few miles away.
Beck praised the calm of the employees, 13 women and one man who are in their 20s to 40s, as they faced three men armed with handguns.
“The detectives have universally commented on how composed they were and how brave they were,” he said.
The chief said detectives watched surveillance videos, interviewed witnesses and collected evidence. Four arrests were made Friday and Saturday in Los Angeles, according to the Los Angeles County sheriff’s website.
Troy Marsay Hammock, 29, of Los Angeles, was arrested on suspicion of robbery and was being held without bail for allegedly violating parole, Beck said.
Everett Oneal Allen, 24, of Los Angeles, was arrested on suspicion of robbery and was held on more than $1 million bail.
Rochelle Monique Sherman, 33, and Paula Roneshia Bradley, 29, both of Los Angeles, were arrested on suspicion of being accessories after the fact and remained jailed on $100,000 bail each.
Raymond Sherman Jr., 34, of Los Angeles, was arrested in Phoenix, Ariz., on suspicion of robbery and was held without bail.