This sounds unfair and to a degree, it is. However, the practice probably would reduce the number of hate and religious shootings.
Exile only means that they have to leave the country, it doesn't mean they go to prison.
It could apply only to hate and religious killings (not mental freaks).

I do think some shooters would think twice if the actions affected their families. Just saying.

Why stop there, what about his or her kindergarten teachers? His or her dentist? Proctologist I mean who know what was said between them?
You cannot help who you are related to, you are not responsible for their actions once they reach the age of majority.
Or do you want to take this all the way and say well, Christ died for their sins anyway so you have to forgive the bastard anyway.

If I hurt someone then my children, grandchildren ,wife etc. Should be kicked out of the country to stop MY behaviors? I must not be understanding the intent of this post.

Don’t see how punishing the boy for the sins of his father, to reference some text from somewhere, does any good.

How does that help anything?

The offender could be mentally ill and therefore need treatment. Retributive justice achieves nothing.

No, that is ridiculous. I am not the least bit responsible for my relatives actions anymore than you are responsible for your relatives actions.