I could have stopped it under normal circumstances. But many factors prevented me from acting. One, it was clear that Albus was welcoming his death. Two, the hallows were making it very hard for me to do anything productive in this case. I was already beaten and bruised. The battle against the Spellbinders took its toll on me. My Shoulder was radiating pain and my hip was letting me know that it didn’t like all this movement. 