The San Jose Mercury News suggests police are dealing with professional criminals in a jewelry heist:

Someone forced entry into an adjoining business that did not have an alarm and then broke into the jewelry store by smashing through a common wall, [Los Altos police Detective Sgt. John] Korges said.

He said that, due to the amount of labor the burglary required, it appears more than one person was involved.

Once in the jewelry store, the suspect or suspects used commercial-grade tools to penetrate the safe, taking between $350,000 and $400,000 of loose precious stones and jewelry left for service and repair.

It reads like there are no leads yet other than it was someone who knew what they were doing with the safe.