Mrs. Claire didn't need to glance up to know who barged into her office in that manner. Over there was her son heaving like a wounded lion. And he was angry. Well, she expected it and was well prepared.
Damon didn't want to let go of Nessa nor did he mean to hurt her, but knowing she's part of his mother's scheme - his mother was using her unknowingly - he had to let go of her. No, he had to avoid her since he had no idea what her mother had seen in her.
What had that crazy woman been thinking, locking her up with him on the night of the full moon? On a night where she knew he was more lethal than a man with a gun? A night when he was at his primal state? Damon bet she would have covered up the murder if he had mistakenly killed Nessa.