I'm not sure who has made this suggestion to you but I'd go back to them if I were you and challenge what their logic is behind it. Are they imagining a huge fearful deity who will punish an innocent soul for someone choosing to practise the craft (rather begs the question why not smite the witch herself...?) Or perhaps some kind of negative karma? I'm getting the impression that whoever told you this has a rather naive view of witchcraft and almost certainly is fearful of it, hence the association with punishment and death. Many witches use their powers for the sole purpose of furthering the "good" (bless them..!) so there would seem to be no logical ground for such an extreme consequence.
I have to say that such a question does suggest you have some fears/concerns, possibly about becoming a witch? If that is the case, I would strongly recommend that you spend some time deciding if this is something you genuinely want to do. Don’t rush into anything. Take the time to dispel any doubts you have.
And should you or anyone you know decide to become a witch and finds a family member suddenly drops dead, don't worry, there really is no link. Don't worry that there has to be a meaning in every coincidence - there doesn't.