The man's suspicion of the situation being a scam was sparked by the refusal of one of the bettors.
He voiced his concern with the words "I think this is a scam".
Despite the refusal of one bettor, two others gave him five dollars.
The man was wary of the situation and thought it might not be legitimate.
The refusal of one bettor only strengthened the man's belief that it was a scam.