A New Jersey man is accused of using dating websites to scam women out of $2.1m (£1.7m) while claiming to be a US soldier stationed overseas.
Prosecutors are using social media posts of Rubbin Sarpong, 35, bragging about his wealth and holding wads of cash as evidence against him.
One of his alleged victims killed herself after transferring more than $90,000 to him, court documents say.
Mr Sarpong, a Ghanaian citizen with US residency, faces wire fraud charges.
Since January 2016, Mr Sarpong used websites Match.com, Plenty of Fish and Ourtime.com to fool more than 30 unsuspecting women into sending him money, according to prosecutors.
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Working with people in Ghana, he is accused of claiming to be a US soldier in Syria who had been awarded gold bars by the military. Prosecutors say he told his alleged victims their money would be returned once the bars arrived in the US.
"Unfortunately, we live in an era where every contact we have with a stranger online must be viewed through the lens of scepticism," the FBI's Gregory Ehrie said.
"Fraudsters are constantly searching for ways to separate people from their money in order to reap a profit while putting forth little effort."
Pictures include one of him holding a stack of cash to his ear like a phone with the caption "making a phone call to let my bank know am coming", and other photos of him with jewellery, electronics and cars.
In one video on his Instagram page, he films himself opening a "money gun" which shoots out bank notes.
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At a court appearance on Wednesday, a judge dismissed his claim he could not afford a lawyer.
Mr Sarpong's fianceé, who attended the hearing, did not speak to reporters about the case afterwards.
None of Mr Sarpong's alleged co-conspirators have been charged. He faces up to 20 years in prison if convicted.