"It said it found dirt on me and that I had something on my wife - but I'm not married so I kind of laughed it off," he said.
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That anonymous letter came in the mail last week - with the writer using the alias BlueGene14.
"I know about the secrets you've been keeping from your wife and from everybody else. More importantly, I have evidence of what you've been hiding," Melgar read aloud.
The sender asked for $15,000 via bitcoin or else they'd publicize Melgar's "secret." It wasn't until he posted the letter on social networking site Nextdoor that he realized other people had also been targeted.
"I spoke about it with my friend and we realized this could be happening to anybody. God knows how many people have received this letter," he said.
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In fact, many of his neighbors said the personalized letters have been circulating for years. But the so-called blackmailer raised his ransom rate.
"I think it's a numbers game for him, and it's just sad to see people have to go this low to try to make something out of their life," Melgar said.
Melgar hopes other people don't fall for the lies and get scammed into giving thousands of dollars to a criminal.
The LAPD said this scam is another on a long list that people need to know about.