Gabriel Duncan was a psychotic teen in the Fifth Season of Smallville, appearing as the main antagonist in the episode "Hidden".
Gabriel was a former assistant editor for the Smallville Torch who worked along with Chloe Sullivan and even contributing to Chloe's Wall of Weird. Gabriel was the computer wizard at the Smallville Torch. Unknown to anyone, Gabriel had a deep hatred of individuals that had obtained metahuman powers after coming into contact with meteor rocks after the meteor shower that struck Smallville.
He was persuaded by his father, an Air Force colonel, to take up a mission to exterminate all of Smallville's meteor-enhanced individuals. His father had created his own Wall of Weird in his house covering the walls with newspaper and magazine articles and clippings detailing the effects of the meteor rocks on the town.
However, some time after Gabriel had graduated from high school, a second meteor shower hit Smallville and his father had developed metahuman abilities. The colonel urged Gabriel to kill him and find a way to rid the world of metahumans. Due to his computer skills, Gabriel had been accepted into MIT but instead of leaving town, he followed through with his father's plan. First he took several documents and access codes that his father had left behind. These codes allowed him to enter a nuclear missile silo located beneath Smallville.
Gabriel strong-armed his way into the missile launch facility and forced the guards to turn over their keys. He then shoots the two guards and used his computer hacking skills and the guards' keys to initiate a launch sequence, setting the launch for one hour. His plan was was to launch a missile directly onto Smallville, destroying the entire town, wiping out its metahuman residents and destroying all remaining meteor rocks to prevent further mutations. He then called Chloe who was packing to move to Metropolis University and was happy to hear from Gabriel. He warned her to get out of Smallville before it was destroyed, wanting her to survive so that she could tell the story of his "heroism".
Chloe tried to enlist Clark's help as she knew about his secret but he had recently lost his powers, so he could not investigate every missile silo in the county. Chloe called Gabriel and tricked him into coming out of hiding by telling him that her car had been totaled and she couldn't get out of town. Gabriel met with Chloe out on a roadside but was confronted by Clark, who demanded to know where he had been hiding. Gabriel pulled a gun and shot Clark, who was no longer invulnerable and was mortally wounded when the bullet passed through his lung. Gabriel then forces Chloe to go with him and leaves Clark bleeding to death in the middle of the road.
Inside the missile silo, Gabriel tied Chloe to a chair and explained his plan and motivations to her, telling her that "meteor freaks" were dangerous and needed to be exterminated. He considered it an act of mercy since he was convinced that no one actually wanted the abilities that kryptonite gave them. He was offended that Chloe didn't agree with his point of view and kept her tied up as the clock ran down. However, Chloe was able to loosen her bonds and free herself, attacking Gabriel and knocking him out.