What should I do if the Executor of my parents trust is found keeping a major amount of money from the benificeries?

There was a account that was not in the trust and should have gone through probate court, but did not. I was sent all the court papers by the executors Lawyer stating the money from my mothers life insurance benifits in my fathers name would be sent through probate court. Since I have been sent a account balance every month since my fathers passing I have known it was still there and had not gone through probate court. I asked the Executor about this money and was told it was rolled into a IRA account and then split between the my sister and I. This was a lie. He has held onto this money. He has also emptied the bank security box that had many gold and silver coins and has not distributed them. What can I do ?