‘Now the children of Benjamin heard that the children of Israel were gone up to Mizpah.'
This is a parenthesis. It would hardly seem surprising as they met on Benjaminite territory. But the statement ‘had heard' probably means that they had received the call and had refused it. It was in fact a grave mistake not to have made more effort to ensure the Benjaminite leaders were there, for had they been there and agreed the verdict the problems that resulted may not have occurred. Trying to force an opinion on people without their participation is a recipe for disaster. Of course if the call to the assembly went with the parts of the concubine's body that may explain why they did not come. They were offended.
‘And the children of Israel, said, ‘Tell us, how did this wickedness happen?'
The leaders who had gathered together now commenced the case, and asked for details of what had occurred. There would presumably be present as witnesses the Levite, his servant and the old man from Gibeah.