Ex-manager calls me and claims I hacked his personal company

I left my last company in December. I worked on many subsidiaries as a sole-developer, and built a PoC for a startup. For one particular project, I noticed that medical data was publicly accessible online. I inquired about this fact, and was told that my predecessor (who worked at the company for four months), didn't know how to code. I knew this application needed a complete rewrite, but was swamped with work - my Trello board had around 100 pending items. I continually brought up the fact that this application was insecure, and that 10k patients records for surgeries, (some events including really personal information like miscarriages) was publicly accessible. I took a short break from the company out of stress. Once I returned to the company, I brought up this issue again. The CEO's son (my manager) flamed me for bringing it up, and ended up screaming that he "didn't care at all about the patient data at all". After this event, I decided to leave, as my morals did not align. At the company I was also asked to complete tasks way outside my job description (software developer), such as ordering signs for the front desk, completing IT support for all branches, and using Photoshop and Illustrator (which I had to learn) to produce marketing material for the company. There were some days where I would have to work until 4 am, then get into work (via a 1.5 hour train journey) the next day. I felt my presence wasn't being respected, however was paid a decent sum. Don't get me wrong, I gained a lot of great experience at this company, but felt it was a toxic environment, where problems could not be brought up. 6-months later (a few days ago), my past manager called me up on the phone. The first call he rang me and told me "I was a dead man", the next phone call he explained who he was. He was extremely angry, and nonsensical. He claimed that I "hacked" his personal company, and that he had proof. He also claimed that he didn't care if I affected my previous employer, but coming after him would be dangerous. To reiterate, I had never been anywhere near his company, nor the company's since my departure. I called the police and filed a report, to ensure he didn't attempt to take legal action against me, despite having not done a single thing. This company has been one of the worst experiences in my professional career.