&gt;I&#x27;ve seen the evidence of the texts in question.<p>Is this smartphone? If so, ensure its not a rooted device, where users can insert&#x2F;delete things as they want.<p>--
Let me add another view. Involve HR and talk to him first. If he admits truth then ask him to resign. If he didn&#x27;t accept, listen to his version of story and ask him for proof. Then decide.