I've had that happen to me before... Lost a 7.5" motoro due to a bite inflicted by my 18" Endlicheri. Took a huge chunk of it's disk... biting right through the ray's organs!
Wesley, I suggest you move the ray out from your main tank... with your ray's wound being raw & fresh like that... your bichir (or other fish) can easily sense or smell it... it may just may take another snap at it once it's hungry again?!!... if not another fatal bite, it might just be enough too overstress your ray to death?!!
Keep a close eye on the tank the next couple days and GL! 
Wesley, I suggest you move the ray out from your main tank... with your ray's wound being raw & fresh like that... your bichir (or other fish) can easily sense or smell it... it may just may take another snap at it once it's hungry again?!!... if not another fatal bite, it might just be enough too overstress your ray to death?!!
Keep a close eye on the tank the next couple days and GL! 

