From Mingpao:

青年文化評論人邵家臻表示，時下青少年流行「聯群結隊」的玩耍文化，朋輩間喜歡各自找朋友加入一起活動，人數有時多達 20至30人，這種行為稱為「搭棚」。他指「搭棚」的朋輩間關係非常疏離，各人互相認識不深，容易產生衝突，往往因言語或爭女朋問題而起爭執，甚至可能有 人因長相「騎呢」而成為眾人取笑或圍攻目標。

There're good sides and bad sides of 搭棚 activity. The good side is increasing the networking, knowing more ppl. The bad side is leading to violence, like what the news described. I think it rarely happens among educated ppl. But you never know what others are thinking. Intentions...