It depends on what it is. If someone is being physically harmed I would go to law enforcement immediately. For "lesser" legal issues, like harassment or fraud,

It depends on what it is. If someone is being physically harmed I would go to law enforcement immediately. For "lesser" legal issues, like harassment or fraud, or anything that could blow back on me, I would get an attorney and document everything, then go to HR or law enforcement. If you're just uncomfortable then talk to your boss about it and ask nicely. That usually works, but if it doesn't there's always a two week notice (assuming this situation is too bad to ignore). Best of luck. I hope things work out well for you.