This is probably more appropriate for the dedicated Charlie Kirk thread, but I like you autists better than the madhouse that's the Kirk thread.
TLDR:
He believed Kirk was wearing a very thin metal plate armor, possibly titanium, since it offered the best balance between concealability and bullet resistance.
One of the downsides of metal armor is that, while very strong, acute angles can deflect a bullet into another part of your body. Plate carriers or spall guards can mitigate deflections or spalling/fragments, but Kirk was probably not wearing those since it's more bulk. Other types of armor, like ceramic, shatter on impact, bleeding the energy away and preventing most fragmentation. The downside for those is that's they're very bulky.
In the video, there seems to be a hole/impact to Kirk's right shoulder, then the bloody neck wound. Video guy notes there was no exit wound from the neck shot, and the neck wound was much larger than you'd expect from a direct hit. That is, the entrance wound is a small hole, while the exit wound would be a larger, bloodier mess.
So the bullet hits his armor and deflects upwards, probably now deformed and possibly traveling sideways. The angle could suggest the reason why we don't see an exit wound is because the bullet never left his body, and is still probably lodged somewhere in his skull.
At least it was quick and painless
