Vampires—through Dean's story, the Howlers including Kai knew Rickle was one, one of the founders of NIRV.
Although because of their small run-in with these creatures, Kai had almost completely forgotten about it, and he remembered once he realized the knee-jerk reaction his body had to Rickle's presence.
He started to think back to all the situations where the group had encountered vampires of sorts.
Marie and Olivia being the first, then there was also the vampire Gary had encountered in the jail, and there was Rickle as well.
'We have no idea of their numbers or their purpose. When I try to dig information it's almost impossible,' Kai thought.
'Is it some type of power they have? It might explain how Rickle was able to obtain all of this information as well.’
'The main concern I have is if there's something to worry about. Midwak talked about them as well, and said it was the main reason why the Lupus Gang was unable to act.'