The worm-like creatures burst out of the exit after Zhang Qin Feng screamed at Alex and the others. Unlike Alex and the other guy looking at the door from the start, the two soldiers positioned by the door were shocked by the monsters pouring out from the exit.
Luckily, those that were coming out of the door were the younger creatures from the pack. Attacking straight on was all they knew how to charge forward like a cannonball attack like the older one.
Their jaws and teeth were also weaker, making the effort of trying to bite or drill through concrete walls and steel almost pointless. But human flesh won't be a problem to them, even if it was fortified by the Steelskin buff provided by the Physique Serum.