I'm currently posting this with TornTools enabled.
If you look at the attack log, you'll see Boxer being attacked at 13:28:58, and 4 seconds later (at 13:29:02) they started an attack of their own while the first fight was still going.
https://www.torn.com/loader.php?sid=attackLog&ID=82692159cc79556e825008509986e21f
Was it always like this?
Is this a Halloween thing?
Or, effectively, a bug?