No.
What are you trying to say? Are you saying that you met him accidentally or unexpectedly somewhere? Did you travel somewhere with him?
If you're talking about meeting him unexpectedly then you are probably looking for "I came across my former boss". However, there has a been a very recent thread on here about that very phrase (sorry, I can't find the thread). I would personally not use "come across + a person" but there were other opinions.