People are born with the ability to connect to the nature but they usually loose it at a very early point. Some when the egg becomes a zygote, some at a later stage of the pregnancy, and some, but very few, lose it after they're born and the ability is not developed, from the sole reason it isn't known. But once, there were people who knew how to take advantage of these powers, and to use them for their own good. Some, controlled the Air, allowing themselves to break the laws of gravity and hover in mid air during their daily activities. Others, who controlled fire, made it easy to create and use fire for different things such as cooking food, and warming themselves. Some of these people also controlled Earth and Water; Earth in order to build houses, caves, and water, known as a healing element, was used for such matters.
But there is one more quality known to man. A quality that is so vicious, and so destructive, that it caused most of the biggest wars in the human history.
Envy has caused to those who couldn't control the elements to want to destroy them and erase them from the world, saying they weren't human, that they were witches and warlocks, saying that they were monsters. Finally, in a few decades, there were almost no elementals left, and these who were left were sent to the underground, hiding their abilities and never exposing them to the others. But as the years past, the stories about the elementals became legends, stories that were told to children before bedtime, Myth. What they didn't know was that these humans were still there, among them, the simply didn't know that they've had these powers.
As the 20th century came, and with it the two greatest world wars, people have started to realize they've had these powers. These people named themselves "The Seconds", since, they were the second lineage to have fond the powers, and use them. But, knowing the legends that appeared to be their new history, they kept themselves underground, collecting all people who they knew had some powers, or even knew about them.
Now, at the 21st century,with the new technology, they have started kidnapping kids with possible genetic order that implied on being an Elemental, killing off these who possessed no powers at all, and training these who showed to wield the powers of the elements.
These kids were The Seconds kids, and their grand kids, trained to believe the normal human wants to kill them and depress their kind, they grew up to be killing machines, without any judgmental abilities. Well, most of them did.