According to NYT (cw: gift link to live report with details of shooting) the moments before the shooting were even more fitting:
Video posted on social media shows the moment Charlie Kirk was shot and the seconds leading to the incident. Kirk was being asked questions about mass shootings in America.
“Do you know how many mass shooters there have been in America in the last 10 years?” a person asks. “Counting or not counting gang violence?” Kirk responds right before he is shot.
ETA Additional context: The person first asked how many mass shooters were transgender in the last ten years, Kirk said "Too many", the person said it's five, then asked the question about total mass shooters. I could infer it as an attempt to compare the two relative to amount of right-wing outrage over the gender identity of shooters.