I'm a California real estate attorney and broker and deal with violations for my local association. Generally, an agent has two business days to modify the status of a property, in this case from active to contingent. This is basically a violation of MLS Rules and may be a violation of the Realtor Code of Ethics.
First, you need to find out what local association the broker/agent is a member of, if any. I see that you're in Fremont. If the property is in Fremont, the person might belong to the Bay East Association of Realtors. If correct, you should contact that association and tell them that you want to submit a complaint regarding this person.
Second, you should also ask the local realtor association what the applicable MLS is. You can then call that MLS and ask to submit a complaint regarding this person as well.
Be aware that this may strain your relationship with the agent, such that the agent will probably not provide you good, if any, competent service and might try to sink the deal. You say that you have a valid contract (the agent's actions might make you question your assertion). But, you don't want to go through the headache of trying to enforce your contract, if you can help it. There is nothing wrong with the agent holding other open houses or trying to obtain back-up buyers, particularly when you still have contingencies remaining on your purchase agreement.
Despite all of the above, you are still obligated to proceed with your due diligence, inspection, and evaluation of the property or to cancel your contract.