For sure you shouldn't yell at that person *you are going to die!!*.
A better approach to the problem is try to ask the person how does s/he feels, suggest a medical examination (sometimes people overlook the importance of regualar checking their health)or to be a bit more cautios when driving, etc, maybe offer to place a blessing on this person?
And remeber that future is not unchangeble.
The advice given here is something I feel right for me and is in Buckland's Complete Book on Witchcraf, in the chapter about divination.
Hope it helps a bit, but obviousely do as you wish. =)