All reports should trigger a thorough investigation of the incident. Your company must not ignore or dismiss these reports. All employees should know that they are expected to comply with all harassment and discrimination investigations. If you are part of an investigation, you are required to be honest and forthcoming AND you are prohibited from obstructing the investigation or retaliating against the parties involved.
Investigations cannot be completely confidential. Some people, including legal counsel, HR, your supervisors, will be involved. And investigating the specific facts with the accused and with witnesses will likely reveal who’s involved in the situation. However, to the extent possible, confidentiality should be maintained. Involved individuals should not discuss the situation or share their involvement in the investigation with any coworkers.
It may not be the victim that reported the incident. No one should disclose who reported the incident to the victim, accused, or witnesses, unless company policy or legal advice says otherwise.