Gundari VS A.O.J Catastor

Both monster have almost same effect that is active it's effect before the damage calculation. But how if the Ally of Justice Catastor attack Gundari or Gundari attack the All of Justice Catastor? How the effects resolve? Here is the answer..

1st situation: If the Gundari attack the Ally of Justice Catastor... Gundari effect will activate first.. this is chain link 1... after that the Ally of Justice Catastor also activate the effect...this is chain link 2... seems the chain link 2 is resolve first.. so Gundari will destroyed by the Ally of Justice Catastor first. Since that Gundari is not on the field, therefore it's effect is not applied on the Ally of Justice Catastor.

2nd situation: If the Ally of Justice Catastor attacks Gundari, it's effect activate first.. this is chain link 1(like above situation).. After that Gundari also activate it's effect...this is chain link 2... same to above situation... chain link 2 is resolve first, so Ally of Justice Catastor will return to Extra deck. Since that Ally of Justice Catastor is not on the field, therefore it's effect is not applied...

Wow!! So confuse.. @.@