What version of RT are you using?
You may want to look at Shredder tool:
“Shredder’s WebUI integrates into RT’s WebUI. You can find it in the Admin->Tools->Shredder tab. The interface is similar to the CLI and gives you the same functionality. You can find ‘Shredder’ link at the bottom of tickets search results, so you could wipeout tickets in the way similar to the bulk update.”
also CLI tool: rt-shredder - RT 5.0.2 Documentation - Best Practical
The question is what you want to happen with any tickets associated with these users?
Shredder can do various things, including set it it to an alternative user. Default use case is that
when tickets are set to “deleted” in RT, they’re not really deleted. Shredder actually removes those tickets from the database, and if the associated user then has no other tickets, this user is deleted as well. (Mostly for data privacy reasons etc. If you no longer have any legitimate reason to keep their personal data, it must be deleted.) Though it’s mostly just rubbish/spam tickets and users this creates that get deleted.