Why did the people cross the river?

From an email from Mom.

Here's a little brain exercise for you:
This is an IQ tester.
The object of the game is to get everyone across the river. This is a test some Japanese applicants have to take when applying for a job in Japan . The odd thing to me is, once you begin taking people across the river, you can't remember how you got them there when you have to start again. Once you begin this test, it's hard to stop. You feel so determined to get these people across.
The instructions are listed below. After reading, click on the link. Enjoy!

http://freeweb.siol.net/danej/riverIQGame.swf

Click on link, and then click on the big blue circle.
Use the rules below.
This is going to do your head in, but it can be done.
Apparently this is an IQ test given to job applicants in Japan : "Everybody has to cross the river".
The following rules apply:
Only 2 persons on the raft at a time
The father can not stay with any of the daughters, without their mother's presence
The mother can not stay with any of the sons, without their father's presence
The thief (striped shirt) can not stay with any family member, if The Policeman is not there
Only the Father, the Mother and the Policeman know how to operate the raft
To start click on the big blue circle on the right.
To move the people click on them.
To move the raft click on the pole on the opposite side of the river.

Have fun! (I failed, you'll probably do better! :-P )