"When the police arrive, detail your discovery, and tell the truth to the authorities."

Do not call the police before contacting your own attorney. You may be advised not to speak to the police at all. Your attorney should probably handle talking to the authorities on your behalf. This is indeed a very difficult situation to handle.

Regarding the privacy policy as it relates to office machines, accessing questionable or illegal material using a personal device through the organizational infrastructure would have to be addressed as well.