I have a need to capture the current logged in user who triggered a webhook, and send that id in the webhook.

I tried capturing the "last modified by" but it gives me id I can't use.

My workflow is like this:

userA owns a contact.

userB causes a webhook to trigger on that contact.  it calls an external script that i use to manipulate the API.

This api call does a number of things, but one of them is it needs to create a case that has the current logged in userB as the owner.  

As it is now, I am only able to capture the "owner" of the contact rather than the user who triggered it.

Is there a hidden method to capture this?

ps: please note, I am using an admin user in my api call, so i don't want that user to be the owner of the case either even though they would be the creator of that case.

Thanks,

Rachel