Move Attachment from CO to Incident

Content

I am trying to use shareFile method to share one of the attachments in a Custom Object to an incident. However, I am seeing an error in the Error Log indicating that the key doesn't exist.

 The record with key 'fattach.file_id' = 21 does not exist in the database.

Here is the snippet of code that I have in the Incident create CPM.

$fattach = $myCustomObject->FileAttachments[$index];

$incident->FileAttachments->shareFile($fattach);                          

Can a CO attachment be shared with incident? If not, how can I make a copy of the attachment into incident object?

Thanks,

SJ 

Version

18D