By the time Cass arrived, Tonks had realised that there wasn't any real danger. The screaming student hadn't done her ear drums a favour, but for the most part, as the professors started filtering in, she realised that she was the threat, not them.
So she'd placed her wand in her holster and held her hands away from her body so they could tell she wasn't going to attack. Feeling a bit like a freak in a circus, she tried to find a familiar face so she could at least attempt to explain, but there weren't any. Even the professors were different, and what had been worry not five minutes before was now turning into full-blown panic.
Tonks let out a sigh of relief when a member of the Auror department spoke up, but that relief was cut short when she realised she didn't recognise the name. "I'm Nymphadora Tonks," she said carefully, not appreciating the wand, but it wasn't as if there weren't others pointed at her as well. "I'm with the Auror department as well. I'm sorry, I've no idea how I wound up here, I think--" She shook her head. "I don't know. I'm not going to hurt anyone, promise."