Tenant2 bit by Tenant1 dog wants to come after landlord

[Robert L.]

I got a letter from Tenant2's lawyer who is investigating an incident where he said Tenant1's dog bit him.  

I talked to Tenant1 and she said his story is not correct and will testify as necessary to defend the landlord from any wrongdoing.  
This all occurred inside the house: why did Tenant2 decide to live in house if he knew about Tenant1's dogs!  

Tenant2 was trying to break up a fight between his dog (not in the lease) and her dog (the approved dog in the lease).  During that breakup, he got bit and now he wants to make the landlord liable?  That's hogwash!

Does this guy have any case whatsoever to try to sue the landlord?  

Tenant1's dogs are: (1) hound (2) mutt

Tenant2 was added to the lease this year but has since moved out of the house