ATLANTIC CITY, N.J. – 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.