At the ending of the episode Kenny and Jane got into a fight, the sort of fight that only one person walks away from. It would seem that Jane took it upon herself to prove to Clementine how unstable Kenny was and so she decided to hide a new born baby in a car by it self and act as if it was killed by walkers [zombies] as she was trying to escape them. Imo Jane being a loner for so long had gotten a bit attached to Clementine and was content that the she ,AJ and Clem would survive just fine without Kenny, its sad though as together they would have stood a greater chance of survival but unfortunately two strong personalities like Kenny and Jane could never agree. Kenny not knowing what had happened and blaming Jane for letting baby AJ die, snapped and the two began a fight to the death. During the fight Kenny manages to pin Jane down and was holding a knife over her attempting to drive it through her chest and you were given the option to shoot Kenny or look away