Bensalem police charged Alexander Salter Jr., 60, of Trenton, with endangering the welfare of a child.
Bensalem Public Safety Director Fred Harran said Salter left his grandson around 3:30 p.m.
"No air was on," Harran said. "No keys in the car. No water."
The youth was quickly spotted, Harran said, and by 4 authorities had tracked down Salter inside the casino.
"I don't understand it," an incredulous Harran said late Thursday. "It's been all over the media. How people aren't wise to it . . . 24 years I've been doing this job, I can't figure people out."
Police said Salter's car was parked illegally, which drew the attention of casino security. After discovering the youth, they found Salter.
"This is a hot day. Grandpa was inside, gambling away," said Bucks County District Attorney David W. Heckler, whose office approved the charges against Salter. "He is now in custody."
Salter was arraigned Thursday night via video conference and then released on $25,000 unsecured bail.
For Parx officials, some of whom had just finished touting new security measures at the news conference, it was another public relations bust.
"This is being handled by the police department," Parx spokeswoman Carrie Nork Minelli said in an e-mail. "We are not releasing any personal information - the man has been evicted from the casino and will no longer be admitted at any time."
But for two state legislators from Bensalem - who want such behavior prosecuted as a felony - the arrest aptly underscored the urgency they had declared to reporters.
"We were all shocked when we first heard of these incidents," State Sen. Robert M. Tomlinson (R., Bucks) told reporters just hours before Salter's arrest. "When we learned there were several more, we were even more shocked and couldn't believe what we were hearing."
