Mark was/is the founder of Facebook?

If Mark is going to an Invester (when Facebook was just made by him), then how would he introduce himself? 'Sir, I am Mark. I am/was the founder of Facebook?'

Mark was/is the founder of Facebook?

If Mark is going to an Invester (when Facebook was just made by him), then how would he introduce himself?

Sir, I am Mark. I am/was the founder of Facebook.

I am confused about the usage of was/is for something that is still true. Here is another example:

My father was/is the architect of this house.

Which one should I use?