Right since the dawn of time the gunslingers were known to be the protector of the dark tower. The gunslingers were men highly trained and respected, men who stood for one thine, justice.
For years the tower which the gunslingers dwelt in was in peace until the man known as the man in black arrived. The man in black was a master in the art of sorcery whose mission was to bring down the dark tower. The dark tower held the forces of evil in the clouds, it prevented them from coming down and the man in black was determined to set them free so he could control them with his sorcery.
But to do that he needed to suck powers from kids with gifts, kids who had magic in their veins and send it directly to the tower to weaken it's foundation and bring it down to the ground.
It wasn't hard for the man in black to take over the tower from the Gunslingers as just two words "stop breathing" from him could send a man to the after life.
The man in black killed all the gunslingers except for one. Chris Shaw has been blessed from birth with the ability to resist every magic. Chris had watched the man in black kill every of the gunslingers including his father. He watched as the minions of the man in black dominate the place he once pledge allegiance to save with his life.
The prophecy had for told the coming of the man in black and the gunslingers had all prepared for that day and had all vowed to die rather than see the dark tower fall but everyday as the man in black sucknin more power in to the dark tower, it foundation weakened and the last gunslingers' hope became slimmer. He knew he didn't stand a chance against the man in black as he was faster than the speed of bullet itself.
So the gunslinger watched the tower fell and the sky turned blood red and in came in the forces of evil along with forces of good. The gunslinger watched as both forces fell from the sky, each ready for battle.