Since an event receiver is attached to a specific event, it's only normal that the event needs to occur before the receiver can be executed.
That being said, to execute an ItemUpdating/ed event, obviously your list item should be updated.
On the other hand, if you own the code base yourself, you should
- Separate your code, so that your executing code accepts a ListItem or Dictionary object which would be the same as which your EventReceiver has access to
- Call this executing function from your eventreceiver, or call the same function from PowerShell, with the necessary parameters (listitem, dictionary, ...)
Long story short: no, you cannot trigger the event receiver itself without invoking it's event first.