The gunshots drew everyone inside and they realized that the person responsible for those shots was not even conscious.
Corey recognized him immediately, he was one of the people that he had sent out and never came back.
This couldn't be a coincidence because there was a huge bite mark around his neck, blood was everywhere but he seemed to be delirious as he couldn't distinguish the living from the dead.
Everyone ducked for cover but Corey put a bullet right between his head without hesitation.
This created panic in the camp as Corey initially thought it was a weapon wound but upon closer inspection, he realized that it was a bite mark.
There was no way a zombie could sneak up on his men so it had to be the evolved zombies he heard so much about, he had fought them once so he understood that they had this skill.
It had been a year since he saw one so there was no telling how much stronger they had become.