He was... [The reindeer trails off. How much of this is okay to tell her? It was an incident they managed to keep fairly isolated, and he's not sure he has the right to start dishing out the dirty laundry.]

[But...she's a trusted friend. It should be okay...right? He swallows and chooses his words carefully.] Something got into his mind and started controlling him. It made him attack people he really cared about...it wanted him to kill u - [A sharp intake of breath] - them. We had to fight him to get rid of it...but it should be gone now.