Why did Dean snap his phone into two halves?

He was absolutely furious that the BMoL had Sam. 

I mean, look at his face right after that:

I’d be veryyyy afraid if I saw Dean Winchester that pissed at me. 

But here’s an interesting thing. Someone asked Emma Peterson who works on the show about the phone and this was her response:

So Jensen just straight up broke that phone in half with his bare hands. Go, Jensen! (X)