An untrained person squatted 300 pounds? I doubt it. And if he did, I doubt he went all the way down. The squat is a very difficult motion to get right, especially if you've never done it before, and I don't think anyone could get 300 pounds on their first try. Even if they had the strength, they wouldn't have the coordination.
Maybe he leg pressed 300lbs.
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<BombScare> i beat the internet
<BombScare> the end guy is hard.