What actions to take when the co-founder has a mental breakdown ?

The technical founder has a mental breakdown and wants to exit the company. He's the main person who developed the software and the whole team is freaking out. The mental breakdown was caused by his personal issues and we've been struggling to straighten him out for the past 3 months. We tried again and again to help him , we even took him to a therapist and even the therapist said "it's better to keep him at the hospital for a couple of days for observation" . He didn't want to stay there because he'll be labelled as mentally unstable. Now we don't know what to do ? He wants to leave the company when we're getting clients and we're about to crack a deal with the investors . This is breaking the company apart.