You can't edit a tweet. You can delete but not edit. He's been caught out and rather than fess up and say he'd gone too far he's coming out with the "I was hacked/it was edited" bollocks.
From Twitter Help pages:
"[Can I edit a tweet once I post it?]
Nope. Once it’s out there, you can’t edit it. You can delete an update by clicking the trash icon..."