I'd sit the team down and say, "There's a lot of stigma attached to this stuff. But when you put all that aside, it's really no different from having a broken arm fixed. If you took time off for a broken arm, and came back with the arm whole, we'd expect you to be the best worker you can. And we'd have empathy if and when your arm got tired. Bob is coming back as a fully functioning member of our team.
"I don't want you to treat him differently. Treat him like we always have. Does anybody have any concerns?"
Some might have concern he will "go nuts and kill somebody". Look at it this way: When he left, did he do anything to threaten or hurt anyone? Then there shouldn't be a concern. Don't assume there are now sudden considerations that were never part of the equation before. If the workers have problems, tell them come and talk to you first. Make clear you expect to hear nothing about the employee being ostracized.
Ask yourself— are you at risk, or is that just what you think of when you hear mental illness? Check your own assumptions against his prior behavior and even his future behavior. Ask the employees to hold him in appreciation and acceptance.
Try this exercise: the next five times you see the returning employee, be aware and very conscious about what's in your head. Check what you're thinking against how he is behaving. If there's a difference, then your assumptions are off. Are you afraid of what you think he's going to do, or what he's actually doing?
And of course, reassure the employees that if he did "snap" you'd act immediately, just like you would if any of them risked the safety of other employees. You're committed to a safe work environment for all employees.
Good luck.