I hope you're talking about the original The Jackal. That's a great movie that has fascinated me essentially because of the theme you've identified. A truly motivated, highly-intelligent person could commit horrendous acts without detection. So far, whoever committed this assassination has succeeded; but I suspect, there is simply too much surveillance in 2025 to get away with it.

edit: regarding the surveillance issue, wonder what the retention on google earth/maps logs is for the location of the shooting?