Call police and no more litter ? Wah.... like that the next time someone throw stuff to my ledge, i call police straightaway. I always "suffer in silent" and clean up the mess.
shouldn't clean up the mess.. must leave the scene 'untouched' so that the cops can dust for fingerprints and check for DNA from the stuffs.. not forgetting to take note of the weather and wind speed of the day the litters were discovered cos they might want to do a 're-enactment' from different floors to determine where the culprit threw the rubbish from...