I would step away if its not in your job title to oversee his work and let the chips fall as they may.unless of course you have a direct work connection with him/her that interfers with your job function. there can be alot of legal issues involved with firing someone or accusing someone of alleged drug activity that you may have to face with your organization, thus just giving you more stress and anger. something you certainly wouldnt want to be involved in as it could damage your own employment. in my situation, it was my job to hire/fire employees and make sure safety was in place.