Absurdly quick ending

No matter how implausible the story was, I was interested and expecting the story to run its course, and I thought Koteas would be playing an interesting part in the last third of the movie. Instead the movie absurdly ends in a quick action scene!

It is not merely "bad", it makes me think that they ran out of budget or some other problems?? Because if this was part of the script I don't think it would have been accepted beforehand? The movie is just 1 hour and 25 minutes or so, and the feeling is that 30 minutes are missing, especially the way it is paced, building up slowly with a lot of scenes involving the children, for example when they found that secret place behind the wardrobe. But that turned out to be insignificant, because suddenly they just kill the movie in an action scene? And the whole premise behind everything is revealed, which turns out to be a ridiculous premise (concerning the murder).

So I would like to know if there is any "behind the scenes" info on the movie if anyone knows anyhting? A documentary about this movie would be interesting, how it went from start to finish, the whole thing seems a mystery to me.