At this point, he highly dislikes the other security guards. Other than that, he doesn't know that Jerry is mentally handicapped;; he didn't really try to personally get to know/recognize the guy in a cramped elevator filled with dead bodies and a giant monster. I'm going off of the thought that Jerry is in his security guard garb, or something similar, so Jack just saw another guard - albeit larger than the others.

Other than that, eh, Jack isn't necessarily good, but he isn't bad. He's more of a neutral character, with a penchant for doing good things, and doing bad things when it's necessary.