User blog comment:DiegoAnime3000/Yang vs Tifa Death Battle/@comment-25405817-20151021025617/@comment-24994749-20151021033808

There is the thing that killing in the heat of battle is not like killing in cold, even if you know the person you are killing is a criminal.

During No Brakes, team RWBY was fighting to get the WF out of their way so they could make it to the locomotive, they didn't precisely have time to think "if I throw this person of the rails they will die", it's also perfectly possible that the fall itself shouldn't be lethal, nd the Grimm flooding the tunnel wa ssomethign that happened on the go. And then they got straight up thrown into battling the Grimm that broke into Vale. The scene at the end of Breach probably took place at the sunset of the same day of the battle. And then you have to account they probably got little to no sleep the previous night. So, by V3 closing, what just happened had not quite settled in their heads.

It's possible we will see them going over it during V3.