parents' reaction at the end..? odd

She had been missing for so long that they pretty much knew she was dead. Hearing the cops finally confirm it was sad, but also a relief, to finally know what happened. So the sadness, relief, the confusion (because it didn't make sense that the neighbor girl would do this) all the conflicting emotions hitting them at once... it leads to kind of a strange reaction. Often times when people have too many emotions to process at once, they just seem blank like that, and over the next few days they'll cry, scream, shout, etc. as they process each emotion individually.

To add to the above, people react differently to news of the death of someone they love. If you watch any of the true crime shows, police are suspicious of every reaction to a loved one's death.

Stoic? Too unemotional. That's suspicious.
Wailing and crying? Too emotional. That's suspicious.
Crying but not hysterically? Looks like manufactured tears. That's suspicious.

I have experienced it myself as I had to bite down on a maniacal laugh that tried to come out when I was told of one of my grandmothers dying.

There is no single right way to react.

If I want to hear the pitter patter of little feet, I'll put shoes on the dog. 

I was like that when I was first told of my grandmother's passing in 1975, and the same as when told of my father's passing in 1982. I was completely numb from head to toe...I had no reaction. But, it hit like a ton of bricks a little later...once I could actually let my brain process it. I didn't want to believe it.

"Ain't life grand!"

I definitely thought the parents reaction to finding out that their DAUGHTER(highlighted because this is their child we're talking about,not a stranger) is in fact dead was odd.Their reaction reminds me of suspects in tv shows like Criminal Minds and Law And Order(To all the short bus riders.Iam NOT saying her parents are in any way suspects).Later on they showed the scene with the mom going into her daughter's room and she starts crying.They also showed the dad crying really hard in the next scene.I think it's a good thing they showed both of those two scenes because like I said before IN MY OPINION the parents first reaction to being told their child was killed seemed odd.