My immediate thought was that someone managed to get an access key, stuffed a ton of data in there, and then was doing a ridiculous amount of egress. That was the only way I could conceivably coming up with anywhere near that much cost.

I doubt AWS has capability to do anything to generate $2T of charges, even if one user maxed every billable capability of every resource they have.

If I got an email with that amount I would've just laughed at the incompetence that lead to a bug that lead to me getting the email. But I write as a backseat email recipient.