You are not recommended to call the police back just yet. At this point, they might already be considering you a suspect of a criminal case. Before you proceed, it is better to consult with a criminal lawyer first to determine what you are supposed to say to the police. This is due to solicitor-client confidentiality, which protects your secrets from being released to the public by your lawyer.
If you return the call and talk to them at once without hearing advice from a criminal lawyer, there is a great chance that you might slip up and say the wrong words. Since they might be considering you a suspect already, your words may even be used as evidence against you. A lawyer can deal with the police for you and even protect you from the police.