My theory uses some of whats been said. Tricking the system so it can time travel. There are parts that lead me to think this. One, it must eliminate the person its replicating. Two, the guard scene. It replicates the guard, then uses a spike. Heres where the theory comes. That spike it used gathered necessary genetic material so it perfectly replicate the guard. Otherwise the skin would look like skin painted metal. Synthetic skin if you will. Its fake skin, but it appears real, down to the molecular level.