While I generally do support the right of people to bear arms, I think it's reasonable to make an exception for stupid people.
"A Hazleton man was charged with leaving a loaded firearm in a men’s room at Mohegan Sun at Pocono Downs casino. "
"State police said the firearm, a .45-caliber, had a full magazine with a round in its chamber."
You can read the whole sad tale HERE. Maybe he was afraid that one of Hazelton's many illegals would try and steal his winnings once he returned to Lou's lair.
As a side note, I've heard that it is illegal to bring a firearm into Pennsylvania casino. Given the amount of money flying around at casinos and the extreme security that no doubt already exists in such places, I'm thinking that's not an unreasonable rule.