Continuity mistake: In the scene where after Peter gets his diploma and has a chat with Gwen, he is carrying a backpack on both shoulders. As the scene continues it switches to one shoulder then both several times. (00:15:50)
Visible crew/equipment: In the scene when Spider-Man is chasing a truck stealing OsCorp's plutonium vials, the truck, driven by Aleksei Sytsevich, crushes one of the police cars. The scene cuts to the left side of the truck crushing the police car. A moment later, it cuts to another angle. Here you can see the camera equipment on the left side of the truck. (00:08:20)
Continuity mistake: After Electro launches Spidey against the police car, the huge dent on the door gets smaller between shots. (00:55:40)
Continuity mistake: During the battle between Electro and Spidey, the chip on Electro's head swaps from being on the right side to being on the left. It is specially noticeable when Electro overloads.
Continuity mistake: When Electro's face appears on the building's windows, he produces huge holes on the pavement, which is empty except for a police car. After Spider stops by the water tank the aerial shot shows the street jammed with cars. (01:49:25)
Continuity mistake: After the blackout when the plane lifts up, Gwen is standing next to Spider-Man, with her left hand on his back. She is just 20cm smaller than him. When the shot changes she is now standing away from him and he is 40cm taller. This changes back and forth. (01:47:25)
Continuity mistake: On the plane, when Peter's father holds the mother's hand she has a small red notebook next to her. When the angle changes it has swapped to a huge red book. (00:03:15)
Answer: Peter could have webbed him up and called the police anonymously.
MasterOfAll
Very likely. However, there was a deleted scene in which Peter, out of anger over Gwen's death, almost beats Harry to death.
Yes. We also see Goblin getting knocked out when all hell breaks loose, and the gears all break apart. Chances are, Peter just webbed him up. (Although, as the other response says, he also got beaten up in a deleted scene.)
TedStixon