I first thought it was Cris because she was the first one up the stairs to the door with the electric shock and Kam was behind her. Somehow Kam gets to the door first and shocks himself. It just seemed like she wanted him to get there first. Probably because she knew Dontae died by touching a shocked door handle and she didn't want to get shocked. lol
From then on I just had a gut feeling about her. As Dwight from the Office would say she was the one I "most medium" suspected. So I believed it was her.