Apparently it’s the ‘professional’ way to do it, and it’s pretty terrifying if you’re a potential target of someone with the resources and desire to do something like this. It is almost impossible to defend against, except perhaps by making the consequences of attempting or succeeding not worth the cost to anyone who might be interested and able. I think this is generally the US approach, but looking at the past it clearly isn’t 100% successful.

The US Secret Service has had several folks who aren’t worried about consequences sneak through and severely injure - or depending on your pet theory regarding JFK - kill presidents.