Flex :: Reference To ArrayCollection And Add Event Listener

I got a reference to an arrayCollection and add event listener like this:
collection.addEventListener(CollectionEvent.COLLECTION_CHANGE, onCollectionChange);
That's fine. Now some other component does have the same reference and is adding items to and removing items from that collection.

Each time the handler is called:
private function onProjectPersonsChange(event:Event):void {
if (event.kind == CollectionEventKind.ADD) {
//do something
} else if (event.kind == CollectionEventKind.REMOVE) {
[Code] .....
Why the removed item is not in 'items'?