Mind control is being enhanced all the time.
So, it is hard to say "perfected."
But it is for a whole lot of purposes.
Anyone's mind can be hijacked at any moment.
Once under control, your mind can be used to do a lot of different things including kill you!
So, depending on what technology may have been used, the killing of Supreme Court Judge Atonin Scalia did not have to be by 50 year old heart attack gun technology. And, he did not need to be in Texas for it to happen. Of course John Kennedy had to be in Texas, because that is where his killers wanted him to be when they killed him.