email.addAddress of current user

I am writing a script include.

I am trying to add the Address of the user who created the request.  How do I add the sys_created_by or sys_id email of the person who created the request?

if(current.getValue('u_drop_off') == '1' {

    var dropOff = gs.getProperty('Location');

    email.addAddress(dropOff);

    email.addAddress(EMAIL OF THE USER WHO CREATED REQUEST);

}