I heard of Kirk years ago because just like Ray Comfort he engaged in the idiotic idea that the Banana proves God, and was so ignorant as to not know that bananas as we know them were created by man, by genetic manipulation of original fruit, which had different appearance and colour (purple).
My recent exposure to him has been on youtube, where he posts videos (I don't watch these), but many skeptics do videos refuting his rubbish and I have watched some of these.
He is a fairly minor entity of the right, so his shooting was probably mainly a target of opportunity. Not to engage in conspiracies, but his murder could also be a false flag operation designed to further enflame an already unstable MAGA mob.
EDIT: I got my Kirks mixed up; it was Kirk Cameron with the banana. They are easy to mix up, as both have same fan base.