Answer:
Grendel's mother attacks Herot because she wants revenge for the death of her son. When she leaves, she ends up taking his arm that is hanging.
I’ll probably lock the doors and the windows so that they can’t escape and leave 1 door open and hide and wait for them to come because that’s the only way they can escape one’s they arrive I’ll shoot them with my potato gun and make them clean up the whole library:)