that is not true.When anyone is born they are born muislims.And they practise different religions according to their compulsions.After their death they are again muslims.So praying for the victims is not unislamic.
We believe Islam is the true religion and you have been given a chance to understand it.Message will be send to all during their life.To accept or not to accept is your wish. But when you die you become a muslim and you have to bear the punishment of your deeds when you were alive n not after your death.
