- "That girl's got so many guys tailing her, she should qualify for Secret Service protection. " - Van to Jake Pollen 
Van McNulty was the son of Lieutenant Ray McNulty, a Marine recruiter who was sent to inform Mrs. Fordman that Whitney Fordman was killed in action but was himself killed by Tina Greer while impersonating Whitney. 
With Tina Greer already dead, Van sought vengeance against other metahumans by hacking into Chloe Sullivan's database and found a list of suspected metahumans. He shot and killed Leonard Wallace, a mechanic with a stretching ability, in the fall of 2003. He left a meteor rock with the word "freak" scratched in the side near the body. 
Van continued hunting "meteor freaks" when he subsequently shot and killed his friend Jake Pollen, a student with amphibious abilities in the pool at Smallville High, saving Lana Lang in the process. Next he tried to kill Lex Luthor, who was in Chloe's database because he had survived so many near death experiences. Van failed to kill Lex when Clark Kent intervened, Clark catching the bullet and subsequently getting Lex to safety, but he learned that Clark was bulletproof but allergic to meteor rocks when Clark tackled Van as he tried to escape and was exposed to the meteor rocks in his backpack. 
Now aware of Clark's weakness, Van created meteor rock bullets and shot Clark, but Clark's parents (Jonathan and Martha) were able to extract the bullet. With the roads out of Smallville all blocked, Van asked Lana for help escaping the police, reasoning that she'd understand how dangerous the "freaks" were after all her experiences with them. When Lana expressed disapproval for his shooting of Lex and grief for his shooting of Clark, stating that Clark was more human that Van would ever be, Van labeled her a "freak-lover" and abducted her. Using a police radio, knowing that Van monitored police channels, Clark invited Van to a showdown where he had seen the picture of Van's father. 
Van met Clark at the school, Clark having the seen the picture in Van's locker, taking Lana along to prove to her that Clark was a freak. He emptied an entire clip of meteor rock bullets into Clark, but he was unaffected. Van and Lana were both stunned, but Lana took advantage of the opportunity and subdued Van with a couple of well-placed kicks. Clark revealed that he was wearing a lead plate to protect himself from the bullets. Van was sent to Belle Reve for his crimes. 
At Belle Reve, Van met Ian Randall and Eric Summers and teamed up with them to take Clark Kent down. Van got a piece of meteor rock smuggled in. After he explains its uses, Ian splits in-two while Van is weightlifting. They then murder Van by ganging up on him while he is using a benchpress, crushing his neck with the very weight that he is using. Ian then quips, "Well you should know better than to trust a meteor freak." 
- In forging the kryptonite bullets, Van created one of the most efficient methods of killing Clark in the entire series. This episode is one of the very few where Clark truly comes the closest to dying, showing and proving the bullets' effectiveness. It's almost certain that Clark would've died if it hadn't been for his parents' timely intervention.
- In a sense, Van is responsible for Lex's future path into villainy as his actions resulted in Lex first becoming aware of the possibility of the meteor rocks causing mutations in others and started his research into creating superhuman soldiers.