Chronicle

The three humans came into contact with an extraterrestrial piece of matter. The matter somehow affected the three guys,  and they began to evolve, just as an animal that comes into contact with unsuitable living conditions and is forced to rapidly adapt. At first the three guys were overwhelmed by the sensation,  and were injured in the process. The evolutionary process occurred in its entirety during the time they were unconscious, which is second in speed and evolutionary efficiency only to bacteria; in comparison, we believed it took several thousand years for us to evolve from homo erectus to homo sapian. In adapting to the foreign substance, they therefore defend themselves against further bodily harm from this alien substance,  which also led to a few consequences.  The most prominent addition to their natural capabilities lies in the form of mind control over matter. Philosophers have inquired that there is a separation of mind or soul and the material word,  which some believe is constantly being manipulated by the mind. Maybe just for the fact that everything we know and experienced is just a collection of senses and neurotransmitters firing off.  The mind paints a picture so vivid we simply ignore its source. The guys past time every day by sharpening their matter bending abilities. One way or another,  one of them listened to his animal instinct more and become an alpha predator,  or an animal that is friends with no-one and only thinks about itself and its own survival. He instinctly loses touch with his human side,  since he is more evolved and probably technically not a human just as a human is not a primate.  His mind is superior to that of a human,  and it gives him an unimaginable advantage in battle ; just as humans have used our superior intellect to rise above all other animals. Being of an entirely different and superior race, its understandable why the rogue one felt his acts of violence towards humans were acceptable; the same level of grief a human might feel while killing a small defenseless animal for food.  I believe owning a higher level of intelligence pressured him to put survival above all other desires,  including the desire to care and love for others, especially those of another, inferior, race.  The truth must be that surviving is the most important and relevant desire,  and the will focuses itself entirely on expending all the bodies resources to further the beings superiority to its surrounding environmental residents. At this moment of him realizing his alpha predator tendancies he became an instant threat to all life on earth,  which is why he needed to be elimanated and his cousin had no choice but to put him down,  just as an out-of-control animal would be put to sleep. Its my person theory however that he became an alpha predator merely because of his human past experiences with bullies. His whole life he was forced to feel inferior,  and he understands fully how dangerous it is to his physical as well as mental state to remain inferior. Once he achieved and realized his power,  there was absolutely no going back to a life of inferiority. The other two evolved beings lived a life of superiority even as humans,  which is why they felt not the need to be extreme or desperate in their means of survival.