This one is a little out of character for WWE and really solidifies the idea that Alberto Del Rio really pissed someone off in doing whatever he did that caused his release. (Or, if you're conspiracy-minded, that he isn't actually fired.) WWE's official Twitter account posted the following messages in reference to Del Rio being let go yesterday:
(1/2) @VivaDelRio is responsible for his own actions. If you’re angry at anyone, be angry at Alberto.
(2/2) There’s no excuse for a pro athlete not to conduct themselves in a professional manner.
WWE has never been one to address moves in this manner, but the very terse wording of the initial release announcement seemed out of place as well. That they referenced his Twitter account is a little odd too; it could be seen as either a way to directly make him aware of what they were saying (as you are notified of any direct mentions to your Twitter handle) or that they're still promoting him for some reason.
The latter may suggest to some that Del Rio is actually still employed and that this is some kind of angle where they're working the fans, except that WWE has always been very clear when releases or punishments such as Wellness violations are announced on WWE that they are not storyline. If this is a change in policy, it would seem an odd one and it would seem odd that they would either use his alleged assault against a WWE employee (or make up such an assault, if that's the case) as a kickstart to a storyline. It is worth noting that Del Rio has not, as of the time of this writing, changed his Twitter name from "Alberto Del Rio" which is a WWE-specific name. He has been moved to the alumni section of WWE.com.
All signs point to this being a legitimate firing and not some sort of angle.