In the gospel today, we have mention of an accident that killed 18 people in the village of Siloam. There is no record of this in history but that is hardly unexpected-Siloam or a few Jews would not have been important.
The Jews saw accidents and sickness as punishment for sins. Some people still do. Jesus told the Jews that this was not the case. He didn't tell us why people die in accidents and things but he did say that it was not as punishment for sin.
Jesus goes on to call the people to repentance. For us moderns it is uncomfortable how much Jesus speaks of judgement, hell and God's retribution.
But still, deep in our hearts every human being knows that they shall have to give an account of their life. We can't say we weren't warned!