A masked man who claimed he was armed and had planted four bombs in a casino held police at bay from a shuttle bus for nearly six hours, demanding $3 million before surrendering peacefully early Wednesday, police said.

During the standoff, the man blamed the Showboat Casino-Hotel for the suicide of his brother, who he said was a former employee who developed a gambling problem, according to a person with knowledge of the standoff who spoke on condition of anonymity because he was not authorized by law enforcement to release the information.

A search of personnel records turned up no one with the name that authorities provided to the casino, said Alyce Parker, a spokeswoman for the Showboat's parent company.

The suspect, David B. Kilkeary, 37, of Crofton, Md., surrendered at 4:24 a.m., obeying an order from FBI agents to strip down to his inner clothing, said state police Sgt. Stephen Jones.

"He just gave up peacefully," Jones said.

No guns or bombs were found, officials said.

Police spokesman Sgt. Monica McMenamin said the suspect's "motivation is under investigation and shall not be released."

Kilkeary's public defender, Christopher H. O'Malley, did not immediately return a message seeking comment. Kilkeary, who served more than three years in prison for twice robbing a Maryland bank, was ordered held without bond by a federal magistrate in Camden.

The conflict began shortly after 10:30 p.m. Tuesday, when police received a report of a man with a gun on a shuttle bus outside the casino. The driver fled after scuffling with the man, Police Chief John J. Mooney said, and a passenger also escaped. Three other people who remained on the bus were released a short time later. There were no injuries.

The FBI said in a complaint that Kilkeary told police he had an explosive strapped to his chest that he described as "C-4 on steroids." He had planted four bombs inside Showboat and demanded $3 million in $100 bills, according to the complaint.

Jones said the suspect had planted a suspicious-looking object in a men's room inside the casino but both the device on his chest and the one in the men's room were fakes, authorities said.

A sweep by technicians and bomb-sniffing dogs found nothing else, state police Capt. Al Della Fave said.

There was no indication what eventually prompted him to surrender.

The casino was shut down during the standoff but was allowed to reopen shortly after 5 a.m.

The FBI filed charges against Kilkeary that included threatening to kill people and damage property, and obstructing interstate commerce by extortion. The first count carries up to 10 years in prison; the second up to 20 years. Both carry fines of up to $250,000.

Casino patron Tony Demetro of Atlantic City said he was playing blackjack when Showboat staff fanned out across the casino floor around 11 p.m. and asked everyone to walk outside.

"They locked down all the tables, covered them with plastic covers and asked everybody to leave. It was pretty calm," he said.

Doris Kinsler of Lynchburg, Va., was with her husband and two other relatives in their room on the 15th floor of the hotel, watching television the entire night. No one told them to evacuate or that there was any potential danger, she said.

"I am mad as hell, and I don't care who knows about it," she said. "If this place blew up, we would have gone with it."

Parker said only the hotel tower nearest the van and the casino floor were evacuated after authorities determined they were potentially at risk and were evacuated. She said other areas were allowed to remain occupied because they were in no danger.