BALTIMORE (WJZ)– A Maryland woman vanishes in Aruba and now the FBI gets involved. Authorities say the key suspect isn’t cooperating.

Mike Hellgren has more on the intensifying search for Robyn Gardner.

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Gary Giordano helped Aruban authorities search the beach for his friend Robyn Gardner in the hours after she disappeared. Police say he remains detained as the only suspect in the case.

Gardner– who is from Frederick– met him online and vanished while the two were on vacation. WJZ has confirmed the FBI in Baltimore is involved in the investigation.

Giordano has a troubled past, including protective orders two women filed against him.

A former neighbor–who asked us to conceal her identity–says his behavior with his kids concerned her.

“He was very loud and he seemed to be yelling at them all the time,” Giordano’s neighbor said. “My son would be frightened.”

Aruban authorities say they still have questions about Giordano’s account of events– that he went snorkeling with Gardner in an area known as Baby Beach for its calm waters– and she never made it back to shore.

“A good question to me is, ‘Did they rent the snorkel equipment, the fins or the flippers and the snorkel?'” asked criminologist Casey Jordan. “Perhaps there is a record that they could look into, to determine whether this couple went snorkeling at all.”

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Giordano’s lawyer says his client denies any wrongdoing.

His house is deserted, but there is a sign on it warning visitors they are under constant video and audio surveillance.

According to published reports, Giordano was accused of secretly videotaping sexual encounters with a woman and threatening her. He was never charged in that case.

“He just seemed to be someone you didn’t want to know,” Giordano’s neighbor said.

In their first public statement, Gardner’s family says they’re keeping faith she’ll be found alive.

“I hope you understand that we are being quiet as to not jeopardize the investigation. Please continue to pray for Robyn.”

According to the Associated Press, investigators in Aruba believe that if Robyn Gardner would have drowned, her body would have surfaced by now.

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Aruban authorities have sent Gardner’s blackberry to the Netherlands as part of the investigation.