Depends on what you mean with "his assets"? Do you mean the uploader? And what do you mean with "OOTB feature"? Is it the direct publication or the workflow?
The easiest way is definitely the workflow, where you create a new workflow step (process step) where you read the username from the metadata of the asset you are deactivating. And based on that you can use the Mail API to send the email.
It's getting a bit more complex if you want to handle also the direct deactivation (without workflow), because there you would need to listen to the OSGI events issued by the deactivation process (in the OSGI console there is a list of the last events sent).