How did Reiner Braun capture Eren? In the end of Episode 7 Season 2 of Attack on Titan, Eren was about to break Reiner Braun's neck.

Then following that event, the Colossus Titan starts to fall, we see a shot that seems to show that Reiner is above Eren and has grabbed him, and later we hear that Reiner captured Eren. 

What happened in the middle and how did Reiner Braun capture Eren?
After the Colossus Titan (Bertholdt) fell on both of them, the Armored Titan (Reiner) bit Eren's Titan form in the neck. That was how he got Eren out from his Titan form.