In Terminator Genisys, when Sarah and Kyle go forward in time to 2017, they end up getting arrested by the police and such.
Who they think is John Connor ends up "rescuing" them, only to have it become clear that he's actually working with/for Skynet. The Arnold Terminator, their real friend, then rescues them from him, and they escape.
He (the aforementioned non-Terminator character) then spends the rest of the movie seemingly trying to catch and kill them. It doesn't seem like he is just trying to catch them alive, as he does a lot of stuff in the process that could easily kill them.
So my question is, why didn't he kill them before the Terminator was there, when it was just him and Sarah and Kyle? It seems like he could have easily destroyed them with no problem, but instead he talked to them for a while and lost his chance.