Technically speaking, you are not required to talk to the prosecutor's office even if you are served with a subpoena. Your duty under a subpoena is to appear at a designated place and time, swear or affirm to tell the truth, and truthfully answer questions put to you.
If you have legitimate concerns about your safety (and it sounds like you do), I would suggest talking to the prosecutor right now. If you only role in the case was reporting to 911 it is very doubtful that you would need to testify at all. If you were an eyewitness to some of the alleged crime, you might be called to testify.
The prosecutor has the authority to protect your identifying information from the defendant -- if you notify him/her in advance. The usual axiom that you catch more flies with honey than vinegar applies to prosecutors as well. If you come to them with legitimate concerns about safety they will try to address your concerns as best they can.
If you haven't been served with a subpoena, you are not under a legal obligation to testify. It is possible you may yet be served with a subpoena as subpoenas do not require a lengthy notice. If and when it becomes clear you may be testifying, consider speaking with the prosecuting attorney's office and discuss your concerns. Good luck.
This response is for information purpose only and does not constitute a legal advice. This response does not create an attorney-client relationship.
prior answer is correct. Most prosecutors understand your very common concern and most courts have significant orders in place preventing the charged party from contact with witnesses. Defense attorneys - like prosecutors - may also try to call you. Neither prosecutors nor defense attorneys can "force" anything other than the process of compelling you to proceedings and making you answer questions they pose under oath. FYI: Intimidating a witness and/or witness tampering is a serious offense and expressing your concerns and the reasons for those concerns to a prosecutor may help. The difficulty your question poses me personally is the potential impact of no testimony against criminals who may cause fear to witnesses. Prosecutors need evidence to convict. The real question to me is whether or not you are a necessary witness to convict - and if you are - what can be done to make you feel as safe as possible while you tell the truth to the jury. One way to help put a buffer on this would be to actually hire an attorney to direct inquiries from anyone to. That retained attorney would be exclusively focused on representing your interests and your desires and may be able to help either prevent or substantially limit your involvement.