system
Given the following post, respond as if you're commenting on Reddit:
human
[Zombieland] where the Hell did Columbus get a rifle?

In Zombieland, Columbus tells us his backstory about how he is a reclusive, somewhat cowardly, college student. 2 months into the apocalypse, he has a rifle and he is a pretty good shot. Like a really good shot. I know the answer could be simple- he got one after the inevitable riots occurred and the gun stores were left abandoned. But in that time, it seems unlikely he could survive even a week without that sort of protection. Seeing as he was on college, which is doubtful to let students carry rifles on campus, he was a cowardly recluse, and he couldn't have known about the apocalypse occurring, how did he get a rifle and where the hell did he learn to shoot?
gpt
Making some broad assumptions about his capabilities and location. He probably holed up in his dorm as long as possible during the beginning of the outbreak. Surving the initial hordes subsisting off of ramen and frozen dinners from the other dorms or apartments around. Using stairwells and simple barricades to keep the slow clumsy rotters out. He then used his skills as an avid gamer using lightguns and wii remotes with a target shooting rifle collected from the campus locker room. It's not a powerful gun but enough to kill a zed with an accurate shot. He then ventured out for food and supplies finding a better rifle and ammunition among the dead or in an abandoned big box store like Walmart. 

Or alternatively he had an upbringing that included training with firearms as many American children from rural areas often do. He collected the rifle from somewhere else but already had skills prior to the apocalypse. 

And the third more worrisome option is he was prepared for the apocalypse. Either through LAARP or simple fantasy play he imagined an apocalypse and wrote up the rules for zombie survival beforehand. He is reasonable in shape and knowledgeable despite his unassuming nature. He could have simply been someone that trains for the apocalypse as a joke or for fun and suddenly found himself in a real apocalypse where it came in hand. Sort of like those doomsday preppers but actually effective instead of just planning different murder devices and thinking MREs have an unlimited shelf life.