Due to the sound isolation of the tunnel, and the darkness making it impossible for anyone to see the danger on the other side, the majority of the insurgents run towards the tunnel.
That place was their last hope of actually running away from this monster that seemed to be after blood and lives. A lot of them regrated ever thinking of doing something like this, but it was too late.
Even the Leader and his lackeys seemed to have gotten frightened by the current situation, but different from those guys running away, they were just trying to put distance between them and Eric.
They were able enough to understand that Eric was in a berserk state right now and soon he would be unable to keep up with the current output and surely grow weak.
That would be their moment to actually counter-attack and kill Eric. At the same time, they were trying to undermine the efforts and actions of each other.