My giant danio did the same once his school died off. I had a bit of “Australian Rainbowfish” (which I have been recently informed is a hybrid and not a true species) and the giant hung out with them and the beunos Aires tetras.
Seeing the two next to each other, it’s entirely possible the GT ate the barb (though the bichir could as well). That said, I’m sure the tigers will turn on each other soon enough (I’ve had a lot of bad experiences with them).
To me, the bichir looks like a Senegal. They are one of the smallest (if not the smallest) bichirs, so I wouldn’t expect much growth. Captive bred wild-type usually cap at 8-10 inches long.