Other mistake: In the scene where Nicole opens her locker and a note from David falls out, the handwriting is exactly the same as the seen where Nicole leaves a note taped to the bedroom door for her father. Although the letters are larger, the same applies to the note on the father's vandalized car, which says he's popped both of their cherries.
Other mistake: In the scene where Gary and Nicole are leaving school and Nicole is telling Gary "please don't tell Margo'' when we first see them they are wearing clothes that were worn in the ending then it switches. Keep eyes on Nicole at first her clothes is the black dress with pink shirt underneath and her hair is down, it switches and she's wearing red pants, purple shirt, and hair in a pony tail.
Answer: Not enough information was revealed in the short scene to make any conclusions and there was no concrete evidence that a (dog-related) crime was being committed. There was not even any indication that a dog was present. One might GUESS that David and his friends prepared dogs for illegal dog-fighting or trained dogs to be dangerous, aggressive watch (or "attack") dogs, but there is no proof. "We're here to see a man about a dog" may sound suspicious or shady, but could mean something as innocent as looking for a lost pet. [00:38:36]. There is a second "clue" much later in the movie when Mr. Walker is talking on the phone: "They're running their own cartel and you can't do a goddamn thing about it"? Mr. Walker probably saw some evidence when he broke into their house. While it might be assumed he means a drug cartel, not all cartels are drug-related. But, relating this scene to the earlier one, it appears "We're here to see a man about a dog" is the code for wanting to buy drugs. (The man who answered the door replied, "Does this look like a kennel?") David and his friends/gang appear to have been selling drugs out of their home. [01:15:55].
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