Cap

The man in the cap was watching them from the other side of the park.
They thought he was one of those paedos that their father had warned them about. They continued playing, but kept an eye on the man. He continued to look straight at them. He gave what sounded like a wolf whistle.
Creepy.
They decided to call the police. Clearly the man was a pervert and should be locked up.
The police arrived quickly, taking this kind of thing very seriously.
The man was shocked as he didn't see them coming. He was just standing and waiting for his guide dog to come back.