Of course you should contact him, and/or anyone else you can reach that has relevant information for you. I wouldn't ask him for inside dirt on the HR admin's

Of course you should contact him, and/or anyone else you can reach that has relevant information for you. I wouldn't ask him for inside dirt on the HR admin's tryst in the conference room, but questions about the job, the organization, and the people are charge are certainly fair game. Unless they are trying to hide something or lie to you, and in that case, it is still the right thing to do for you to investigate. People seem to have this belief that potential employer or employee should only contact a small subset of officially sanctioned information channels. A prospective employer shouldn't do something like call your current boss with reference questions without your opinion, and similarly you shouldn't seek information from sources that might put the employer at risk. Take whatever knowledge you gain from contacting him and weigh that against what they have told you. Go back to them and be upfront, tell them the former employee told you X,Y,Z and that you'd like to get their response. A good organization will respect your thoroughness. A bad org will panic and be defensive, and that should be considered as well.