How to terminate an employee with mental health issues?

As in the title, I lead a small company. We currently employ 35 employees. I genuinely care about each and every member of my staff. The people who work for us seem to be happy. We were all doing very well until a few months ago.

In February 2023, we hired John. John seemed like a perfect match for our team. He had the right experience and came highly recommended. The trial period went well, but as soon as it finished, John started calling in sick at least once a week. It became really bad, and he finally revealed that he's chronically ill and also struggles with severe mental health issues. He begged us not to fire him. We talked with his team and decided to give him a chance. We were very accommodating and as supportive as possible. Together with another member of the company, we spent many hours trying to figure out how to best help John in his unhappy circumstances.

Unfortunately, over a year later, this is not sustainable anymore. I will spare you the details, but John's behavior is really bad right now, and it's affecting other staff members. Terminating John's contract seems to be the only solution. We have a great legal team who told us how to handle it from a legal side. However, we are still concerned. It is so bad that we would not be surprised if John decides to harm someone or himself if he finds out that he lost his job. Also, we cannot fire him right away. His contract's cancellation notice is two months so he will be still here for two months after he finds out which is something we all dread. Any advice?