Because Dark's classroom was on the other side of the school, they had a prolonged period before he made it, during which Bernice said nothing. Secretly she was hoping Xander would decide to speak, but she wasn't going to waste her time.
When Dark stepped in, he first looked at Xander, but he, too, was intentionally hiding whatever it was he felt. Then he looked at Bernice, "What exactly happened?"
"He," She nodded towards Xander, "attacked two students in the bathroom earlier. From what I was told, he jumped them without giving them a chance to explain themselves."
"Explain what?"
"They said he misunderstood what they were saying. Xander has not said anything about what began it from his perspective."