Absolutely. It's all mater of statistics. There are so many CEOs of unpopular/despised companies and there are so many people who hate them with homicidal passion.
All it takes if for one of those CEOs get cavalier of personal security and one of his potential killers apply enough training, intelligence and luck.
Something that happened in Dallas six decades ago with an antiquated Italian bolt action rifle being in hands of person with just enough ex-Marine training.