This is right after Conner jumps down to the lower level to get to the grenade launcher and hurts his shoulder. He is crawling away from the T-800 and the shot is from right behind Conner's head. The T-800 is practically right on top of John, but when he shoots the oven and the molten steel lands on the T-800, the shot shows John like 30 feet away.
Reese's introduction isn't the only thing that stays the same about the character between movies. Here he uses his preferred weapon - a sawed-off shotgun. Marcus isn't keen on having a gun aimed at him though, so he snatches it out of Reese's hands, then teaches him a trick to keep that from happening - fashioning a safety strap. Reese puts that same trick to use after he steals a police shotgun in The Terminator.