From the audio, I would speculate that a suppressed weapon was used to shoot Kirk from his left at a fairly low trajectory. It does not appear that a hollow-point round was used, as this would have likely caused more damage at the entrance site, which was the left side of Kirk’s neck.
SOF personnel I have spoken with regarding the shooting estimate the shot may have been taken from roughly 200 meters away.
From: https://sofrep.com/news/conservative-commentator-charlie-kirk-shot-at-utah-valley-university-event/