I have changed the practice area to criminal law, so lawyers who practice in that area can answer. I would say you need to hire a lawyer now who can advise you properly. What the DA might do depends on the facts, but criminal charges cannot be based on nothing more than "belief." So go over the facts with a board certified criminal lawyer, and you will be able to get the answers to make you feel less afraid. I am sorry for your loss.
This is not legal advice. You should always discuss the specifics of your issue in person with an attorney. Be aware that there are time limits on all claims that depend on the kind of claim, so do not delay in seeking an attorney.
Let me first say that I am so sorry to hear about your son. That is truly a tragic event and I can't even imagine the pain and the loss that you must be going through. I have young children of my own and cannot even fathom the pain of losing one of them.
As for your question, there's really not much you can do. If the police continue to contact you and ask you questions then it might be a good idea to lawyer up.
This response does not create an attorney-client relationship between you and I. I am not your lawyer and I am not representing you in the underlying issue stated in your question. The response I have offered is not intended to be relied upon, you should seek out an attorney to assist in this matter.
I too am sorry for your loss. If you are worried and it causes you stress, you could retain an attorney to look into the matter and obtain for you a confirmation that the case is closed. Otherwise, not much you can do, except take what the Texas cops say at face value.
I am sorry for your loss. It can happen that the Prosecutors will reach a different opinion than CPS. Their opinion will be based upon the investigation into the circumstances of the accident. You can request a copy of your file from CPS so you can see the pertinent parts of the investigation then you can review this with a criminal defense attorney.