Continuity mistake: When Peter for some reason decides to try to hoodwink the English receptionist pretending to be "John Hopkins", he mentions that he tried to get Gwen to be part of "my team." In that, a guy comes in frame walking from right to left. Several seconds later, same extra, same walk. (01:24:20)
Continuity mistake: During Peter's rant inside the Oxford office, Emma Stone's hair comes and goes from the front of her right shoulder. This happens all the way throughout the scene, even at the pivotal moment at the very end when she asks him which was the "one thing" he mentioned. (01:23:20)
Continuity mistake: Inside Oxford's North American office, Peter starts blathering; he says "Everything's a mess", he says; Emma Stone in the next shot has her hand raised. The mistake happens again at the end of the conversation when Peter goes "I'm sorry to bother you", and her raised hands go down her sides from the wide shot. (01:23:15)
Continuity mistake: When Harry is talking to Spidey that barely camouflages his voice, the hair on his forehead keeps changing position between shots. (01:21:20)
Continuity mistake: Peter inputs in Google "What is Roosevelt?" and gets as output for his search "Franklyn Roosevelt + New York" (01:01:25)
Continuity mistake: Harry wakes up to Spiderman's voice in his living room. He sits and looks at him. Notice the messy hair on his forehead. Changes shot (he is rubbing his nose like Gwen, just not as cute) and his hair is combed over properly. (01:20:50)
Continuity mistake: Peter comes back home and finds his aunt sitting on his bed staring at his serial killer-like collage. The two start talking, and during the conversation May has several locks of hair on or off the cheek as the two angles alternate. (01:16:45)
Continuity mistake: During the kiss in closet scene, Garfield has his hand on Emma Stone's face abruptly at the cut. Seconds later, when they concur that the kiss was "a bit rushed" they smile at each other with a completely different position - as you can see from the light rays on their faces. (01:10:55)
Continuity mistake: Peter is cooped up in the garage window as he answers the phone after a night of dangerous experiments. First shot and his arms are free, close-up, and he's wrapped in a blanket. (01:05:00)
Continuity mistake: Harry just found by accident the secret interactive desktop from his father. He drags and drops a menu, but somehow when he checks out the item he highlighted, the menus themselves changed entirely showing stuff like "Max Dillon experiment" that were not there a moment before. (01:03:05)
Other mistake: We see Peter freshly printing an old news story from CNN; the timestamp on the visible corner says the sheet was printed at 9:18 AM. The scene takes place in the evening. (01:01:45)
Continuity mistake: Watching the news after his confrontation with Electro, Spiderman picks up from the table the webbing device that got fried. He then throws it back on the table, where meanwhile all the tools shifted around randomly. (01:00:40)
Revealing mistake: Look behind the policeman when he shouts "Sir, get your hands away from the cables, right now." For absolutely no reason the extras (one in particular to the left that was looking in a different direction entirely) remembers to act scared only at the word "get", but the policeman already started shouting before, and sparks have been flying even earlier. (00:52:00)
Continuity mistake: A policeman spots the suspicious guy accessing the high voltage cables and screams "Get out of the way." There's a macroscopical continuity error here with an extra sporting a peach colored jacket that 'gets out of the way' twice in two separate shots and with completely different timing. (00:52:00)
Other mistake: Car alarms are annoying; Electro sets off every car alarm in the street, once he silences a single one draining power off the batter, every other alarm stops too - despite the lights still flashing. Incidentally, in the rest of the movie Electro shows his power on a much larger scale but never sets off any car alarm or makes headlights blink. (00:48:35)
Continuity mistake: Peter and Gwen are having a spontaneous reunion. Gwen tried her new laugh on Peter, and she's laughing at his positive reception of it saying "It's not adorable." Notice by her a dude with thin framed glasses and a beige jacket that walks past them. A few seconds later when she does the nose rub thingy, the same guy is again passing them by. (00:47:15)
Continuity mistake: Playing with stones by the river (the GPS coordinates on scree are a perfect match for Pebble beach), Harry says "I tried to forget everything about this place." Peter is scratching his chin, but in the next shot his hand is nowhere near his face or even in frame. (00:42:05)
Continuity mistake: The two friends are chatting from opposite sides of the riverside railing. Peter says "Yeah"; look at the folded hat in his pocket. Next shot, he adds "I don't know" and the cloth is wrapped in a different way than before. (00:41:30)
Continuity mistake: Harry Osborn says at the business meeting that everyone will work for Felicia; Felicia's hand position in close-up is egregiously different from the one she has in the view of the table. (00:38:30)
Continuity mistake: At the meeting, Harry says "What was Dad thinking?" The lawyer with the purple bowtie is looking at him, hands off the table, but in the next shot he has both hands on it. Same a few seconds later when Harry says "Hi" to Felicia; hands on the table first, off the table in the reverse angle. (00:37:35)
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