Ok this sick man wants to commit suicide with a 19 yr old girl... please help?

A man I know is planning a suicide death pact thing with a 19yr old girl I know. He is a former police officer and former pastor... but has some serious issues we are in michigan and he is trying to get her to come up in a few weeks to hang together and die as they ____.... is it my duty to contact the police or is it legal? PLEASE I really want to know what to do...