Our ex business partner decided to steal our website after

Our ex business partner decided to steal our website after he was dismissed as an employee for gross misconduct. He is also 50% shareholder. He was dissmised on the 6th of June and our website crashed on the 7th of June. Our web developer,was the only person except us who was able to log in and make changes. We found him via ex business partner who I believe asked him to take our web site down. On the 9th of June we had several customers complaining about our website being down. We called our developer he said that he will look into this but later. Somehow couple of hours later I have managed to log in and I found a lot of evidence that it was done by our webdeveloper and ex business partner. My question is - what should we do in this situation?Also they deleted all our content and transferred our website to another hosting which I think is not only illegal but can be a criminal offence?