Investigation isnt a term owned by a government agency or degree of offending. I can investigate my little toe if I want.

Companies have internal investigations that must be followed either by policy, and often by law. They’ll have a duty to shareholders to complete the investigation.

Your open/closed assessment is false. It’s kinda clear you’ve never dealt with staff and human resourcing issues before? Or if you have it hasn’t been in a firm bigger than a few people.