How to trigger the error start event?

Regarding the docs [1] the current path of execution is ended and an error is thrown when the process execution arrives at an error end event. This error can be caught by a matching intermediate boundary error event.

But the example given in the picture does not have an intermediate boundary error event. Instead it contains an error start event. My question here is: How to trigger the error start event?

There is also a note withing the picture saying: “The error is completely handled by the subprocess”. But the documentation of the error end event does not state that it will trigger the error start event. So how does the error get handeled then?

[1] https://docs.camunda.org/manual/7.3/api-references/bpmn20/#events-error-events-error-start-event

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