Leave it to law enforcement !
My read of one possible view is that the physical confrontation with the guy downstairs was over and each departed the scene back to separate residence ...it is not clear at all if a gun was involved in first confrontration at all.
It is entirely possible that wife totally over reacted and is seekng to,reverse engineer a defense for stabbing somebody twice in the back.....leave that one to law enforcement !
What is perfectly clear is that young man needs some very serious professional help as to his depression and his alchohol abuse ...I think our combat vets deserve extra special benefit of the doubt ....but they need to be involved in addressing their problems ....we owe an extra effort to our vets , and I m not sure,those services are available in every community. ..To the extent you can, push drag or otherwise get the young man to some professional help.