You really have to be up close and personal. Then too, what size .22 was he hit with and how far away was the shooter? Most “assassination” guns are .22’s - the Israeli Mossad uses them. A .22 will whiz around your brain box scrambling it.
22 were used for assignation pistols only because of the ability to very effectively silence them.
They can be effectively silenced because they are so low power, lower speed bullet.
You can kill with them. But because they are such low power, it is typical for states to ban hunting with them.