You absolutely MUST speak to this person!
Over the years,through embarassment, lack of courage or an inability to find the "right moment" 3 pilots I knew ended up dead (in one case killing a pax as well.) The guilt lives with me to this day. Every one can point at someone in their club who is reckoned to be the next accident and yet doesn't do something about it. If you are this close to a fellow pilot you owe it to them their family and yourself to bite the bullet.
Good luck
Sir George Caley
The air is a navigable ocean which laps at everymans front door