Even if no action taken now, if more and more people come to report same incident and the number accumulate then there will be time for management to take action since the reputation is more valuable than that single worker.

Report to upper management might be more appropriate I think

I have no experience in this but perhaps others do. I would report to the management where the guy work so that if they think necessary will take immediate action. Depend on how they judge your story. Maybe few others already complained and the case is mounting. The management will have immediate access to any report involving their employee.