Before capitalism took hold of Halloween and made it all about which Disney character you're going to buy a costume for every year, people had costumes that they made from stuff at home. There was no Iron Man or Moana option. The only thing people could end up looking like is actual murderers. "What are you going to be for Halloween this year?" / "I was thinking of wearing a stocking on my head, the way a very real murderer would, and also leather gloves to cover my fingerprints. A dark jacket to hide in the night too." Everyone just ended up looking like people who would actually hurt you.
Even that kid is terrified. He probably even saw those guys dress up like that and he's still afraid of them. Dad turned into a masked killer within seconds.