I think one of your neighbour did this. I saw a 1 800 number for descrimination hot line before but I did not write it down. Check with the international center and also consult with them. You should also check with your neighbours and ask them if they saw any suspicious people around your house. Have a camera is also a good idea. I once read an article about a balck family who moved into a white neighbourhood. The family's neighbour did many annoy things in order to get rid of the black family from the neighbourhood.